Compositions and methods for crosslinking polymers in the presence of atmospheric oxygen

ABSTRACT

Embodiments of organic peroxide formulations provide significant improvements in surface tackiness (often including tack-free surfaces) when curing elastomers in the presence of oxygen. The peroxide formulations may include, for example, one or more compounds selected from sulfur-containing compounds, organophosphite compounds, HALS (Hindered Amine Light Stabilizer) compounds, aliphatic allyl urethane compounds, and blends comprising nitroxides (e.g., 4-hydroxy-TEMPO) and quinones (e.g., mono-tert-butylhydroquinone).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage application under 35 U.S.C. § 371of PCT/US2015/063615 filed Dec. 3, 2015, which claims benefit to U.S.patent application Ser. No. 62/089,421, filed, Dec. 9, 2014.

FIELD OF THE INVENTION

The present invention relates to compositions and methods forcrosslinking elastomers with organic peroxides in the presence ofatmospheric oxygen, and products made by those methods.

BACKGROUND OF THE INVENTION

Polymers and copolymers crosslinked with organic peroxides are known tohave superior properties, particularly compared to polymers crosslinkedby sulfur cure. These properties include high heat ageing resistance,low percent compression set, decreased staining of metal, and easyproduction of colored products with enhanced color stability. In view ofthese beneficial properties, peroxide cure has a great deal of practicalimportance. A possible drawback of peroxide cure is that air must beexcluded from the surface of a material during cure; if the air is notexcluded, a tacky surface may result, due to cure inhibition by oxygen.

When oxygen comes into contact with an elastomer being crosslinked by anorganic peroxide, the crosslinking reaction at the elastomer surface maybe inhibited, or may not take place at all. Thus, the elastomer surfaceremains uncured. Therefore, curing rubber articles with peroxides istypically conducted in steam tubes, molten salt baths, steam autoclaves,and air-evacuated closed molds, all of which are designed to apply heatto the elastomer while excluding atmospheric oxygen during thecrosslinking process.

Unfortunately, excluding air from these commercial processes involvesconsiderable time and expense. In contrast, sulfur vulcanization ofelastomers can be conducted using lower cost hot air ovens or tubes inwhich hot atmospheric oxygen poses no issue. While the sulfur curativesare generally lower in cost than organic peroxides, the types ofelastomers suitable for sulfur cure are limited to unsaturatedelastomers, e.g., poly(ethylene propylene diene), poly(butadiene),natural rubber, synthetic poly(isoprene), poly(styrene-butadiene)rubber, poly(butadiene-acrylonitrile) rubber and the like.

In many cases, manufacturers would like to switch from sulfur toperoxide cure using existing hot air ovens; however, curing withconventional peroxide systems under these circumstances would not beviable due to the surface cure inhibition by oxygen. Various methodshave been suggested for preventing surface cure inhibition by oxygenduring free radical crosslinking. These methods have, for variousreasons, generally met with little or no success.

U.S. Pat. No. 6,747,099 is directed to elastomer compositions thatinclude bis-, tri- or higher polymaleimides and/or bis-, tri- or higherpolycitraconimides.

U.S. Pat. No. 4,983,685 is directed to elastomer compositions thatinclude at least 2.5 to 20 phr (parts per hundred rubber) ofbenzothiazyl disulfide.

U.S. Pat. No. 6,775,848 is directed to pore-free rubber articlesprepared by dip-molding.

U.S. Pat. No. 4,376,184 is directed to rubber compositions that includean organopolysiloxane gum.

EP 0246745 is directed to elastomer compositions that include lowmolecular weight polymers of 1,000 to 15,000 as an additive.

U.S. Pat. No. 5,219,904 is directed to fluorine-containing elastomersthat contain iodine and bromine.

U.S. Publication No. 2013/0131221 is directed to elastomer compositionsthat include at least one cellulose ester.

Generally, none of the previously described systems have adequatelyprovided a tack-free surface while concurrently providing desirablephysical properties like superior compression. Moreover, previous knownmethods involving sulfur and peroxide cure are limited to unsaturatedelastomers.

Thus, it is desirable to have organic peroxide formulations and methodswhich cure commercially available crosslinkable elastomers and polymers,both saturated and unsaturated, in the full or partial presence ofatmospheric oxygen.

SUMMARY OF THE INVENTION

Embodiments of the present invention relate to organic peroxideformulations that can cure solid elastomers in the full or partialpresence of oxygen using, for example, a hot air oven or tunnel, orsteam autoclave. Embodiments of the invention also relate tocrosslinkable elastomer compositions, processes for curing theelastomers, and products made by such processes.

The applicants have discovered several compounds that can be combinedwith organic peroxides to significantly reduce the surface tackiness ofelastomeric articles cured in the presence of oxygen. Non-limitingexamples of these compounds, which can be blended with organic peroxidesto produce peroxide formulations of the present invention, include:sulfur-containing compounds, organophosphite compounds, HALS (HinderedAmine Light Stabilizer) compounds, aliphatic allyl urethane compounds,and blends comprising 4-hydroxy-TEMPO (4-OHT),mono-tert-butylhydroquinone (MTBHQ), and at least one sulfur-containingcompound. Without being bound by any theory, it is believed that thesecompounds support or enhance the desirable surface cure of elastomerswhen used with at least one organic peroxide in the presence of oxygen.

In accordance with one embodiment, the applicants have discovered thatorganic peroxide formulations having at least one sulfur-containingcompound can significantly reduce the surface tackiness of anelastomeric article that is peroxide cured in the full or partialpresence of oxygen, particularly when the formulations do not includecertain monomeric co-agents. For example, it was surprisingly found thatorganic peroxide formulations that contain at least onesulfur-containing compound, but that do not contain any bis-, tri- orhigher poly-maleimides (e.g., N,N′-m-phenylene bismaleimide, alsoreferred to as HVA-2), or any bis-, or tri- or higherpoly-citraconimides, can virtually eliminate the surface tackiness of anelastomeric article that is peroxide cured in an open air system, andcan also provide high crosslink density, high tensile strength, and low% compression sets. This is contrary to other systems, such as thosedescribed in U.S. Pat. No. 6,747,099, which specifically includes thecostly N,N′-m-phenylene bismaleimide (HVA-2) compound as a required partof the peroxide formulation to provide a tack-free surface in thepresence of hot air while reducing % compression set values.

Embodiments of the present invention relate to an organic peroxideformulation comprising, consisting essentially of, or consisting of atleast one organic peroxide and at least one sulfur-containing compound,wherein the formulation does not include any bis-, tri- or higherpoly-maleimides, or bis-, tri- or higher poly-citraconimides. Theamounts of the at least one organic peroxide and the at least onesulfur-containing compound are selected such that the formulation iscapable of curing an elastomer composition in the full or partialpresence of oxygen (e.g., using a hot air oven or tunnel, or steamautoclave).

Embodiments of the present invention also relate to an elastomercomposition comprising, consisting essentially of, or consisting of atleast one elastomer, at least one peroxide, and at least onesulfur-containing compound, wherein the elastomer composition does notinclude any bis-, tri- or higher poly-maleimides, or bis-, tri- orhigher poly-citraconimides, and wherein the elastomer composition iscurable in the full or partial presence of oxygen.

Embodiments of the present invention also relate to a process for curingan elastomer composition, said process comprising, consistingessentially of, or consisting of curing an elastomer composition in thepresence of oxygen, wherein the elastomer composition comprises,consists essentially of, or consists of at least one elastomer, at leastone organic peroxide and at least one sulfur-containing compound,wherein the elastomer composition does not include any bis-, tri- orhigher poly-maleimides, or bis-, tri- or higher poly-citraconimides.Embodiments of the present invention also relate to products made bythis process.

The applicants have also discovered that organic peroxide formulationshaving at least one organophosphite compound can significantly reducethe surface tackiness of an elastomeric article that is peroxide curedin the full or partial presence of oxygen. Such peroxide formulationscan provide a tack-free surface, or substantially tack-free surface,when curing an elastomer composition in the presence of hot air.

Embodiments of the present invention relate to an organic peroxideformulation comprising, consisting essentially of, or consisting of atleast one organic peroxide and at least one organophosphite compound.The amounts of the at least one organic peroxide and the at least oneorganophosphite compound are selected such that the formulation iscapable of curing an elastomer composition in the full or partialpresence of oxygen (e.g., using a hot air oven or tunnel, or steamautoclave).

Embodiments of the present invention also relate to an elastomercomposition comprising, consisting essentially of, or consisting of atleast one elastomer, at least one peroxide, and at least oneorganophosphite compound wherein the elastomer composition is curable inthe full or partial presence of oxygen.

Embodiments of the present invention also relate to a process for curingan elastomer composition, said process comprising, consistingessentially of, or consisting of curing an elastomer composition in thepresence of oxygen, wherein the elastomer composition comprises,consists essentially of, or consists of at least one elastomer, at leastone organic peroxide and at least one organophosphite compound.Embodiments of the present invention also relate to products made bythis process.

The applicants have also discovered that organic peroxide formulationshaving at least one HALS (Hindered Amine Light Stabilizer) compound cansignificantly reduce the surface tackiness of an elastomeric articlethat is peroxide cured in the full or partial presence of oxygen. Suchperoxide formulations can provide a tack-free surface, or substantiallytack-free surface, when curing an elastomer composition in the presenceof hot air.

Embodiments of the present invention relate to an organic peroxideformulation comprising, consisting essentially of, or consisting of atleast one organic peroxide and at least one HALS compound. The amountsof the at least one organic peroxide and the at least one HALS compoundare selected such that the formulation is capable of curing an elastomercomposition in the full or partial presence of oxygen (e.g., using a hotair oven or tunnel, or steam autoclave).

Embodiments of the present invention also relate to an elastomercomposition comprising, consisting essentially of, or consisting of atleast one elastomer, at least one peroxide, and at least one HALScompound wherein the elastomer composition is curable in the full orpartial presence of oxygen.

Embodiments of the present invention also relate to a process for curingan elastomer composition, said process comprising, consistingessentially of, or consisting of curing an elastomer composition in thepresence of oxygen, wherein the elastomer composition comprises,consists essentially of, or consists of at least one elastomer, at leastone organic peroxide and at least one HALS compound. Embodiments of thepresent invention also relate to products made by this process.

The applicants have also discovered that organic peroxide formulationshaving an aliphatic allyl urethane compound can significantly reduce thesurface tackiness of an elastomeric article that is peroxide cured inthe full or partial presence of oxygen. Such peroxide formulations canprovide a tack-free surface, or substantially tack-free surface, whencuring an elastomer composition in the presence of hot air.

Embodiments of the present invention relate to an organic peroxideformulation comprising, consisting essentially of, or consisting of atleast one organic peroxide and at least one aliphatic allyl urethanecompound. The amounts of the at least one organic peroxide and the atleast one aliphatic allyl urethane compound are selected such that theformulation is capable of curing an elastomer composition in the full orpartial presence of oxygen (e.g., using a hot air oven or tunnel, orsteam autoclave).

Embodiments of the present invention also relate to an elastomercomposition comprising, consisting essentially of, or consisting of atleast one elastomer, at least one peroxide, and at least one aliphaticallyl urethane compound wherein the elastomer composition is curable inthe full or partial presence of oxygen.

Embodiments of the present invention also relate to a process for curingan elastomer composition, said process comprising, consistingessentially of, or consisting of curing an elastomer composition in thepresence of oxygen, wherein the elastomer composition comprises,consists essentially of, or consists of at least one elastomer, at leastone organic peroxide and at least one aliphatic allyl urethane compound.Embodiments of the present invention also relate to products made bythis process.

The applicants have also discovered that organic peroxide formulationshaving a blend of at least one nitroxide-containing compound (forexample, 4-hydroxy-TEMPO (4-OHT)), at least one quinone-containingcompound (preferably mono-tert-butylhydroquinone or MTBHQ), and at leastone sulfur-containing compound can significantly reduce the surfacetackiness of an elastomeric article that is peroxide cured in the fullor partial presence of oxygen. Such peroxide formulations can provide atack-free surface, or substantially tack-free surface, when curing anelastomer composition in the presence of hot air, and can also provideimproved scorch times and cure times.

Embodiments of the present invention relate to an organic peroxideformulation comprising, consisting essentially of, or consisting of atleast one organic peroxide, at least one nitroxide-containing compound(e.g., 4-hydroxy-TEMPO), at least one quinone-containing compound (e.g.,MTBHQ), and at least one sulfur-containing compound. The amounts of theat least one organic peroxide, the 4-OHT, the at least one quinone, andthe at least one sulfur-containing compound are selected such that theformulation is capable of curing an elastomer composition in the full orpartial presence of oxygen (e.g., using a hot air oven or tunnel, orsteam autoclave).

Embodiments of the present invention also relate to an elastomercomposition comprising, consisting essentially of, or consisting of atleast one elastomer, at least one peroxide, 4-OHT, at least one quinone(e.g., MTBHQ), and at least one sulfur-containing compound, wherein theelastomer composition is curable in the full or partial presence ofoxygen.

Embodiments of the present invention also relate to a process for curingan elastomer composition, said process comprising, consistingessentially of, or consisting of curing an elastomer composition in thepresence of oxygen, wherein the elastomer composition comprises,consists essentially of, or consists of at least one elastomer, at leastone organic peroxide, 4-OHT, at least one quinone (e.g., MTBHQ), and atleast one sulfur-containing compound. Embodiments of the presentinvention also relate to products made by this process.

DETAILED DESCRIPTION

The applicants have discovered organic peroxide formulations thatprovide significant improvements in surface tackiness (often includingtack-free surfaces) when curing elastomers in the full or partialpresence of oxygen (e.g., using a hot air oven or tunnel, or a steamautoclave). Therefore, organic peroxide compositions of the presentinvention can replace sulfur vulcanization in cure processes whereoxygen (e.g., atmospheric oxygen) may be present in various amounts.

When heat and pressure are applied to a sulfur-cured elastomer, thesulfur bonds typically break and re-form, causing the elastomer todeform. One test to measure this deformation is called percentage (%)compression set test. The greater the crosslinked elastomer specimenexhibits permanent deformation under heat and pressure, the higher the %compression set value. Thus, lower % compression set values, equating toless or no permanent elastomer deformation, are desirable for manyelastomers, particularly for hose, gasket and sealing applications.

Elastomers that are cured using organic peroxide compositions of thepresent invention may include both solid unsaturated elastomers, solidsaturated elastomers, or combinations thereof. U.S. Pat. No. 6,747,099,which is incorporated by reference herein, discloses the use of organicperoxides in the presence of air. Embodiments of the present inventionprovide improvements over formulations taught in U.S. Pat. No.6,747,099, which do not provide sufficiently tack-free surfaces whenelastomers with little or no unsaturation are used (e.g., poly(ethylenepropylene) (EPM)). For example, embodiments of the present invention canobtain surface cures with blends of ethylene-propylene-diene terpolymer(EPDM) and poly(ethylene propylene) (EPM) (thus significantly reducedunsaturation) substantially identical to those obtained with elastomersthat have high unsaturation, such as EPDM. Thus, embodiments of theinvention are not limited by the unsaturation level of elastomers.

One aspect of the present invention relates to an organic peroxideformulation comprising, consisting essentially of, or consisting of, atleast one organic peroxide and at least one sulfur-containing compound,wherein the formulation does not include any bis-, tri- or higherpoly-maleimides, or bis-, tri- or higher poly-citraconimides.

A second aspect of the present invention relates to an organic peroxideformulation comprising, consisting essentially of, or consisting of atleast one organic peroxide and at least one organophosphite compound.

A third aspect of the present invention relates to an organic peroxideformulation comprising, consisting essentially of, or consisting of atleast one organic peroxide and at least one HALS compound (HinderedAmine Light Stabilizer).

A fourth aspect of the present invention relates to an organic peroxideformulation comprising, consisting essentially of, or consisting of atleast one organic peroxide and at least one aliphatic allyl urethanecompound.

A fifth aspect of the present invention relates to an organic peroxideformulation comprising, consisting essentially of, or consisting of atleast one organic peroxide and at least one nitroxide-containingcompound (e.g., 4-hydroxy-TEMPO (4-OHT)) blended with at least onequinone-containing compound (e.g., mono-tert-butylhydroquinone (MTBHQ))and at least one sulfur-containing compound.

According to particular embodiments, the organic peroxide formulationsof the present invention are capable of providing a completely orsubstantially tack-free cured elastomer composition. As used herein, anelastomer composition that is substantially tack-free has a surfacetackiness of between 7 and 9.9 or 10, preferably between 8 and 9.9 or10, more preferably between 9 and 9.9 or 10. An elastomer compositionthat is completely tack-free has a surface tackiness of 10 and is mostdesirable. A method for measuring surface tackiness is provided herein,and is referred to as the Facial Tissue Paper Test.

According to particular embodiments, the organic peroxide formulationsof the present invention are capable of curing an elastomer compositionthat includes at least one saturated elastomer (e.g., a blend of atleast one saturated elastomer and at least one unsaturated elastomer) inthe full or partial presence of oxygen, wherein the cured elastomercomposition is completely or substantially tack-free.

Organic Peroxides Suitable for Use in Embodiments of the PresentInvention

With the exception of hydroperoxides and liquid peroxydicarbonates, allthose organic peroxides known to undergo decomposition by heat togenerate radicals capable of initiating the desired curing(crosslinking) reactions are contemplated as suitable for use in theformulations of the present invention. Non-limiting examples includedialkyl peroxides, diperoxyketals, mono-peroxy carbonates, cyclic ketoneperoxides, diacyl peroxides, organosulfonyl peroxides, peroxyesters andsolid, room temperature stable peroxydicarbonates. In at least oneembodiment, the organic peroxide is selected from dialkyl peroxides,peroxyketals, cyclic ketone peroxides, monoperoxycarbonates,peroxyesters and diacyl peroxides.

Peroxide names and physical properties for all these classes of organicperoxides can be found in “Organic Peroxides” by Jose Sanchez and TerryN. Myers; Kirk-Othmer Encyclopedia of Chemical Technology, Fourth Ed.,Volume 18, (1996), the disclosure of which is incorporated herein byreference.

Illustrative dialkyl peroxide initiators include:

-   di-t-butyl peroxide;-   t-butyl cumyl peroxide;-   2,5-di(cumylperoxy)-2,5-dimethyl hexane;-   2,5-di(cumylperoxy)-2,5-dimethyl hexyne-3;-   4-methyl-4-(t-butylperoxy)-2-pentanol;-   4-methyl-4-(t-amylperoxy)-2-pentanol;-   4-methyl-4-(cumylperoxy)-2-pentanol;-   4-methyl-4-(t-butylperoxy)-2-pentanone;-   4-methyl-4-(t-amylperoxy)-2-pentanone;-   4-methyl-4-(cumylperoxy)-2-pentanone;-   2,5-dimethyl-2,5-di(t-butylperoxy)hexane;-   2,5-dimethyl-2,5-di(t-amylperoxy)hexane;-   2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3;-   2,5-dimethyl-2,5-di(t-amylperoxy)hexyne-3;-   2,5-dimethyl-2-t-butylperoxy-5-hydroperoxyhexane;-   2,5-dimethyl-2-cumylperoxy-5-hydroperoxy hexane;-   2,5-dimethyl-2-t-amylperoxy-5-hydroperoxyhexane;-   m/p-alpha, alpha-di[(t-butylperoxy)isopropyl]benzene;-   1,3,5-tris(t-butylperoxyisopropyl)benzene;-   1,3,5-tris(t-amylperoxyisopropyl)benzene;-   1,3,5-tris(cumylperoxyisopropyl)benzene;-   di[1,3-dimethyl-3-(t-butylperoxy)butyl]carbonate;-   di[1,3-dimethyl-3-(t-amylperoxy)butyl]carbonate;-   di[1,3-dimethyl-3-(cumylperoxy)butyl]carbonate;-   di-t-amyl peroxide;-   dicumyl peroxide;-   t-butylperoxy-meta-isopropenyl-cumyl peroxide;-   t-amyl cumyl peroxide;-   t-butyl-isopropenylcumylperoxide;-   2,4,6-tri(butylperoxy)-s-triazine;-   1,3,5-tri[1-(t-butylperoxy)-1-methylethyl]benzene-   1,3,5-tri-[(t-butylperoxy)-isopropyl]benzene;-   1,3-dimethyl-3-(t-butylperoxy)butanol;-   1,3-dimethyl-3-(t-amylperoxy)butanol; and mixtures thereof.

Other dialkylperoxides which may be used singly or in combination withthe other free radical initiators contemplated by the present disclosureare those selected from the group represented by the formula:

wherein R₄ and R₅ may independently be in the meta or para positions andare the same or different and are selected from hydrogen or straight orbranched chain alkyls of 1 to 6 carbon atoms. Dicumyl peroxide andisopropylcumyl cumyl peroxide are illustrative.

Other dialkyl peroxides include:

-   3-cumylperoxy-1,3-dimethylbutyl methacrylate;-   3-t-butylperoxy-1,3-dimethylbutyl methacrylate;-   3-t-amylperoxy-1,3-dimethylbutyl methacrylate;-   tri(1,3-dimethyl-3-t-butylperoxy butyloxy)vinyl silane;-   1,3-dimethyl-3-(t-butylperoxy)butyl    N-[1-{3-(1-methylethenyl)-phenyl}1-methylethyl]carbamate;-   1,3-dimethyl-3-(t-amylperoxy)butyl N-[1-{3    (1-methylethenyl)-phenyl}-1-methylethyl]carbamate;-   1,3-dimethyl-3-(cumylperoxy))butyl    N-[1-{3-(1-methylethenyl)-phenyl}-1-methylethyl]carbamate.

In the group of diperoxyketal initiators, the preferred initiatorsinclude:

-   1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane;-   1,1-di(t-butylperoxy)cyclohexane;-   n-butyl 4,4-di(t-amylperoxy)valerate;-   ethyl 3,3-di(t-butylperoxy)butyrate;-   2,2-di(t-amylperoxy)propane;-   3,6,6,9,9-pentamethyl-3-ethoxycarbonylmethyl-1,2,4,5-tetraoxacyclononane;-   n-butyl-4,4-bis(t-butylperoxy)valerate;-   ethyl-3,3-di(t-amylperoxy)butyrate; and mixtures thereof.

Illustrative solid, room temperature stable peroxydicarbonates include,but are not limited to: di(2-phenoxyethyl)peroxydicarbonate;di(4-t-butyl-cyclohexyl)peroxydicarbonate; dimyristyl peroxydicarbonate;dibenzyl peroxydicarbonate; and di(isobornyl)peroxydicarbonate. Otherperoxides that may be used according to at least one embodiment of thepresent disclosure include benzoyl peroxide,OO-t-butyl-O-hydrogen-monoperoxy-succinate andOO-t-amyl-O-hydrogen-monoperoxy-succinate.

Illustrative cyclic ketone peroxides are compounds having the generalformulae (I), (II) and/or (III).

wherein R₁ to R₁₀ are independently selected from the group consistingof hydrogen, C1 to C20 alkyl, C3 to C20 cycloalkyl, C6 to C20 aryl, C7to C20 aralkyl and C7 to C20 alkaryl, which groups may include linear orbranched alkyl properties and each of R₁ to R₁₀ may be substituted withone or more groups selected from hydroxy, C1 to C20 alkoxy, linear orbranched C1 to C20 alkyl, C6 to C20 aryloxy, halogen, ester, carboxy,nitride and amido, such as, for example, at least 20% of the totalactive oxygen content of the peroxide mixture used for a crosslinkingreaction will be from compounds having formulas (I), (II) and/or (III).

Some examples of suitable cyclic ketone peroxides include:

3,6,9, triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane (or methyl ethylketone peroxide cyclic trimer), methyl ethyl ketone peroxide cyclicdimer, and 3,3,6,6,9,9-hexamethyl-1,2,4,5-tetraoxacyclononane.

Illustrative examples of peroxy esters include:

-   2,5-dimethyl-2,5-di(benzoylperoxy)hexane;-   t-butylperbenzoate;-   t-butylperoxy acetate;-   t-butylperoxy-2-ethyl hexanoate;-   t-amyl perbenzoate;-   t-amyl peroxy acetate;-   t-butyl peroxy isobutyrate;-   3-hydroxy-1,1-dimethyl t-butyl peroxy-2-ethyl hexanoate;-   OO-t-amyl-O-hydrogen-monoperoxy succinate;-   OO-t-butyl-O-hydrogen-monoperoxy succinate;-   di-t-butyl diperoxyphthalate;-   t-butylperoxy (3,3,5-trimethylhexanoate);-   1,4-bis(t-butylperoxycarbo)cyclohexane;-   t-butylperoxy-3,5,5-trimethylhexanoate;-   t-butyl-peroxy-(cis-3-carboxy)propionate;-   allyl 3-methyl-3-t-butylperoxy butyrate.

Illustrative monoperoxy carbonates include:

-   OO-t-butyl-O-isopropylmonoperoxy carbonate;-   OO-t-butyl-O-(2-ethyl hexyl)monoperoxy carbonate;-   1,1,1-tris[2-(t-butylperoxy-carbonyloxy)ethoxymethyl]propane;-   1,1,1-tris[2-(t-amylperoxy-carbonyloxy)ethoxymethyl]propane;-   1,1,1-tris[2-(cumylperoxy-carbonyloxy)ethoxymethyl]propane;-   OO-t-amyl-O-isopropylmonoperoxy carbonate.

Illustrative diacyl peroxides include:

-   di(4-methylbenzoyl)peroxide;-   di(3-methylbenzoyl)peroxide;-   di(2-methylbenzoyl)peroxide;-   didecanoyl peroxide; dilauroyl peroxide;-   2,4-dibromo-benzoyl peroxide;-   succinic acid peroxide.-   dibenzoyl peroxide;-   di(2,4-dichloro-benzoyl)peroxide.

Imido peroxides of the type described in PCT Application publicationWO9703961 A1 6 Feb. 1997 are also contemplated as suitable for use andincorporated by reference herein.

Preferred peroxides include one or more of:2,5-di(t-butylperoxy)-2,5-dimethyl hexane; t-butyl cumyl peroxide;2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3;t-butylperoxy-isopropenylcumylperoxide;3,3,5,7,7-pentamethyl-1,2,4-trioxepane; 3,6,9,triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane;m/p-di(t-butylperoxy)diisopropyl benzene; m-di(t-butylperoxy)diisopropylbenzene; p-di(t-butylperoxy)diisopropyl benzene; di-t-butyl peroxide;di-t-amyl peroxide; dicumyl peroxide;1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane;1,1-di(t-butylperoxy)cyclohexane; n-butyl 4,4-di(t-butylperoxy)valerate;ethyl 3,3-di(t-butylperoxy)butyrate; OO-t-butyl-O-(2-ethylhexyl)monoperoxy carbonate; OO-t-butyl-O-isopropylmonoperoxy carbonate;polyether poly-t-butylperoxy carbonate; t-butylperoxybenzoate;t-butylperoxyacetate; t-butylperoxymaleic acid;di(4-methylbenzoyl)peroxide; dibenzoyl peroxide;di(2,4-dichlorobenzoyl)peroxide; dilauroyl peroxide; cumenehydroperoxide; and di(4-tert-butylcyclohexyl)peroxydicarbonate.

More preferred peroxides include one or more of:2,5-di(t-butylperoxy)-2,5-dimethyl hexane; t-butyl cumyl peroxide;2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3;t-butylperoxy-isopropenylcumylperoxide;3,3,5,7,7-pentamethyl-1,2,4-trioxepane; 3,6,9,triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane;m/p-di(t-butylperoxy)diisopropyl benzene; m-di(t-butylperoxy)diisopropylbenzene; p-di(t-butylperoxy)diisopropyl benzene; di-t-butyl peroxide;dicumyl peroxide; 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane;1,1-di(t-butylperoxy)cyclohexane; n-butyl 4,4-di(t-butylperoxy)valerate;ethyl 3,3-di(t-butylperoxy)butyrate; OO-t-butyl-O-(2-ethylhexyl)monoperoxy carbonate; OO-t-butyl-O-isopropylmonoperoxy carbonate;polyether poly-t-butylperoxy carbonate; t-butylperoxybenzoate; dibenzoylperoxide; di(2,4-dichlorobenzoyl)peroxide; cumene hydroperoxide; anddi(4-tert-butylcyclohexyl)peroxydicarbonate.

Even more preferred peroxides include one or more of:2,5-di(t-butylperoxy)-2,5-dimethyl hexane; t-butyl cumyl peroxide;2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3;t-butylperoxy-isopropenylcumylperoxide;3,3,5,7,7-pentamethyl-1,2,4-trioxepane; m/p-di(t-butylperoxy)diisopropylbenzene; m-di(t-butylperoxy)diisopropyl benzene;p-di(t-butylperoxy)diisopropyl benzene; di-t-butyl peroxide; dicumylperoxide; 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane;1,1-di(t-butylperoxy)cyclohexane; n-butyl 4,4-di(t-butylperoxy)valerate;ethyl 3,3-di(t-butylperoxy)butyrate; OO-t-butyl-O-(2-ethylhexyl)monoperoxy carbonate; OO-t-butyl-O-isopropylmonoperoxy carbonate;t-butylperoxybenzoate; dibenzoyl peroxide; anddi(2,4-dichlorobenzoyl)peroxide.

Most preferred peroxides include one or more of:2,5-di(t-butylperoxy)-2,5-dimethyl hexane; t-butyl cumyl peroxide;2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3;t-butylperoxy-isopropenylcumylperoxide; m/p-di(t-butylperoxy)diisopropylbenzene; m-di(t-butylperoxy)diisopropyl benzene;p-di(t-butylperoxy)diisopropyl benzene; dicumyl peroxide;1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane;1,1-di(t-butylperoxy)cyclohexane; n-butyl 4,4-di(t-butylperoxy)valerate;ethyl 3,3-di(t-butylperoxy)butyrate; OO-t-butyl-O-(2-ethylhexyl)monoperoxy carbonate; OO-t-butyl-O-isopropylmonoperoxy carbonate;and t-butylperoxybenzoate.

In accordance with particular embodiments, organic peroxide formulationsof the present invention may further include at least one coagent and/orat least one filler. Non-limiting examples of co-agents include allylmethacrylate, triallyl cyanurate, triallyl isocyanurate,trimethyloylpropane trimethacrylate (SR-350), trimethyloylpropanetriacrylate (SR-351), zinc diacrylate, and zinc dimethacrylate.

Non-limiting examples of optional inert fillers for use in the organicperoxide formulations of the present invention include water washedclay, e.g., Burgess Clay, precipitated silica, precipitated calciumcarbonate, synthetic calcium silicate, and combinations thereof. Variouscombinations of these fillers can be used by one skilled in the art toachieve a free-flowing, non-caking final peroxide formulation.

In accordance with particular embodiments, the organic peroxideformulations of the present invention may include a silica filler.

Organic Peroxide Compositions Comprising Sulfur-Containing Compounds

According to an embodiment of the present invention, an organic peroxideformulation comprises, consists essentially of, or consists of at leastone organic peroxide and at least one sulfur-containing compound. Theformulation does not include any bis-, tri- or higher poly-maleimides(e.g., N,N′-m-phenylene bismaleimide, also referred to as HVA-2), orbis-, tri- or higher poly-citraconimides. The organic peroxide(s) andsulfur-containing compound(s), and their respective amounts, arepreferably selected such that the formulation is capable of curing anelastomer composition in the full or partial presence of oxygen (e.g.,using a hot air oven or tunnel, or a steam autoclave). Embodiments ofthe formulations comprising organic peroxide(s) and sulfur-containingcompound(s) are described in Examples 1-4 and 8-12. Examples 9-12include Vultac-5 formulations of the invention.

Sulfur-containing compounds listed in the “R. T. Vanderbilt RubberHandbook”, 13th Ed. (1990), which is incorporated herein by reference,may be considered for use in the practice of this invention.

Sulfur-containing compounds suitable for use in the present inventioninclude, but are not limited to, organic sulfide compounds, which may bemonosulfides, disulfides, trisulfides or higher polysulfides.

The preferred sulfur-containing compounds used in embodiments of theinvention are those that contain the general disulfide or trisulfidetype structure:

(R¹—SS—R²)_(x) or (R¹—SSS—R²)_(x), where R¹ or R² may be the samestructure or different, and may be saturated or unsaturated; and x=1and/or x≥2 to include polymeric structures, e.g., the Vultac®disulfides. R¹ and R² may, for example, be aromatic groups such asphenyl groups, which may be substituted, such as with hydroxyl and/oralkyl groups; non-aromatic cyclic groups, such as morpholine groups orcaprolactam groups, with sulfur-nitrogen bonds being present; and/orbenzothiazyl groups.

Dimeric and polymeric alkylphenol polysulfides (also referred to aspoly(alkylphenol)polysulfides) are one type of sulfur-containingcompound which may be utilized in the present invention. The alkylphenolmay be tert-butyl phenol or tert-amyl phenol, for example. Suchsubstances and methods for their synthesis are described in U.S. Pat.Nos. 2,422,156; 3,812,192; 3,968,062; 3,992,362; 6,303,746; 7,294,684;and 8,063,155, each of which is incorporated herein by reference in itsentirety for all purposes.

The disulfides and trisulfides may be biobased (e.g., garlic and onionoils) or non-biobased compounds.

Illustrative sulfur-containing compounds include but are not limited to:

Vultac® 5=poly(t-amylphenol disulfide);

Vultac® 7=poly(t-butylphenol disulfide);

Vanax® A=DTDM=4,4-dithiodimorpholine;

Altax®=MBTS=benzothiazyl disulfide also called mercaptobenzothiazoledisulfide;

and

CLD-80=N,N′-Caprolactam disulfide.

In one embodiment of the invention, the at least one sulfur-containingcompound comprises, consists essentially of or consists of benzothiazyldisulfide. In other embodiments, the at least one sulfur-containingcompound comprises, consists essentially of or consists of benzothiazyldisulfide and one or more of a poly(alkylphenol)polysulfide,N,N′-caprolactam disulfide, or 4,4′-dithiomorpholine.

The organic peroxide formulation may, in certain embodiments of theinvention, contain elemental sulfur in addition to the sulfur-containingcompound(s).

According to one of the particular embodiments, the organic peroxideformulation of the present invention comprises, consists essentially of,or consists of:

at least one organic peroxide (for example, in an amount from 20 wt % to99 wt %, or from 30 wt % to 90 wt % or from 40 wt % to 75 wt %, or from40 wt % to 70 wt %, or from 40 wt % to 65 wt %, or from 45 wt % to 80 wt%, or from 45 wt % to 75 wt %, or from 45 wt % to 70 wt %, or from 45 wt% to 65 wt %, or from 50 wt % to 98 wt %, or from 50 wt % to 75 wt %, orfrom 50 wt % to 70 wt %, or from 50 wt % to 65 wt %, from 50 wt % to 60wt %, based on the total organic peroxide formulation);

at least one sulfur-containing compound (for example, in an amount from5 wt % to 50 wt %, or from 10 wt % to 50 wt %, or from 15 wt % to 45 wt%, or from 20 wt % to 70 wt %, or from 20 wt % to 65 wt %, or from 20 wt% to 60 wt %, or from 25 wt % to 70 wt %, or from 25 wt % to 65 wt %, orfrom 25 wt % to 60 wt %, or from 30 wt % to 70 wt %, or from 30 wt % to65 wt %, or from 30 wt % to 60 wt %, or from 35 wt % to 70 wt %, or from35 wt % to 65 wt %, or from 35 wt % to 60 wt %, or from 40 wt % to 70 wt%, or from 40 wt % to 65 wt %, or from 40 wt % to 60 wt %, or from 40 wt% to 55 wt %, or from 40 wt % to 50 wt %, based on the total organicperoxide formulation); and

at least one optional inert filler (for example, in an amount from 0.01wt % to 60.0 wt %; 0.01 wt % to 40 wt %, or from 0.01 wt % to 20 wt %,or from 0.01 wt % to 20 wt %, or from 0.01 wt % to 10 wt %, or from 0.01wt % to 5 wt %, or from 0.01 wt % to 2 wt %, or from 0.01 wt % to 0.1 wt%, based on the total organic peroxide formulation),

wherein the formulation does not include any bis-, tri- or higherpoly-maleimides, or bis-, tri- or higher poly-citraconimides, and

wherein the at least one peroxide and the at least one sulfur-containingcompound, and their respective amounts, are selected such that theformulation is capable of curing an elastomer composition in the full orpartial presence of oxygen, and wherein the cured elastomer compositionis substantially or completely tack-free.

According to preferred embodiments, compositions of the presentinvention that include at least one organic peroxide combined with atleast one sulfur-containing compound do not include any bis-, tri- orhigher poly-maleimides, or bis-, tri- or higher poly-citraconimides,such as HVA-2 (N, N′-m-phenylene dimaleimide).

According to particular embodiments, the at least one sulfur-containingcompound is selected from the group consisting of poly(t-amylphenoldisulfide); poly(t-butylphenol disulfide); 4,4-dithiodimorpholine;benzothiazyl disulfide; N,N′-caprolactam disulfide; and a combinationthereof. According to further embodiments, the at least onesulfur-containing compound includes benzothiazyl disulfide and at leastone additional sulfur-containing compound (e.g., poly(t-amylphenoldisulfide); poly(t-butylphenol disulfide); 4,4-dithiodimorpholine; orN,N′-caprolactam disulfide).

An additional embodiment of the present invention provides an elastomercomposition comprising, consisting essentially of, or consisting of:

at least one elastomer (either saturated, unsaturated, or both); and

at least one organic peroxide,

and at least one sulfur-containing compound,

wherein the elastomer composition does not include any bis-, tri- orhigher poly-maleimides, or bis-, tri- or higher poly-citraconimides, and

wherein the elastomer composition is curable in the full or partialpresence of oxygen (e.g., using a hot air oven or tunnel, or a steamautoclave). Preferably, the cured elastomer composition is completely orsubstantially tack-free.

According to particular embodiments, the elastomer compositioncomprises, consists essentially of, or consists of at least oneelastomer (either saturated, unsaturated, or both); and

at least one organic peroxide (on a pure basis) in an amount from 0.1phr to 20 phr, or from 1 phr to 10 phr, or from 2.0 phr to 7.0 phr(parts per hundred rubber), or from 2.5 phr to 6.5 phr, or from 3.0 phrto 6.0 phr, or from 3.5 phr to 5.5 phr, or from 4.0 phr to 5.0 phr;

at least one sulfur-containing compound in an amount from 0.1 phr to 20phr, or from 1 phr to 10 phr, or from 2.5 phr to 6.5 phr, or from 2.5phr to 6.0 phr, or from 2.5 phr to 5.5 phr, or from 3.0 phr to 6.5 phr,or from 3.0 phr to 6.0 phr, or from 3.0 phr to 5.5 phr, or from 3.5 phrto 6.5 phr, or from 3.5 phr to 6.0 phr, or from 3.5 phr to 5.5 phr; and

optionally at least one additive selected from the group consisting ofprocess oils (e.g., aliphatic process oils), process aids, pigments,dyes, tackifiers, waxes, reinforcing aids, UV stabilization agents,blowing agents, scorch protectors, activators, antiozonants and coagents(e.g., those marketed by Sartomer, except for bis-, tri- or higherpoly-maleimides, or bis-, tri- or higher poly-citraconimides, such asHVA-2). In addition to aliphatic process oils, other oils such asparaffinic, aromatic or more polar or ester type derivatives (e.g., whenusing HNBR or CPE) may be considered depending upon the type ofelastomer chosen. For EPDM, EPM, PE copolymers and blends, the preferredoil is aliphatic.

Non-limiting examples of co-agents that may be used in accordance withany embodiments of the present invention include allyl methacrylate,triallyl cyanurate, triallyl isocyanurate, trimethyloylpropanetrimethacrylate (SR-350), trimethyloylpropane triacrylate (SR-351), zincdiacrylate, and zinc dimethacrylate.

According to particular embodiments, the sulfur-containing compound(s)in the organic peroxide formulation include benzothiazyl disulfide(MBTS). For example, the benzothiazyl disulfide may be present in theformulation in an amount that is less than 2.0 phr, or less than 1.75phr, or less than 1.5 phr, or less than 1.25 phr, or less than 1.0 phr,or less than 0.75 phr, or less than 0.5 phr, or in an amount from 0.01phr to 2.0 phr, or from 0.01 phr to 1.75 phr, or from 0.01 phr to 1.5phr, or from 0.01 phr to 1.0 phr, or from 0.01 phr to 0.75 phr, or from0.01 phr to 0.5 phr, or from 0.1 phr to 2.0 phr, or from 0.1 phr to 1.75phr, or from 0.1 phr to 1.5 phr, or from 0.1 phr to 1.0 phr, or from 0.1phr to 0.75 phr, or from 0.1 phr to 0.5 phr, or from 0.2 phr to 2.0 phr,or from 0.2 phr to 1.75 phr, or from 0.2 phr to 1.5 phr, or from 0.2 phrto 1.0 phr, or from 0.2 phr to 0.75 phr, or from 0.2 phr to 0.5 phr.

According to particular embodiments, the sulfur-containing compound(s)in the organic peroxide formulation include benzothiazyl disulfide andat least one additional sulfur-containing compound selected from thegroup consisting of poly(t-amylphenol disulfide); poly(t-butylphenoldisulfide); 4,4-dithiodimorpholine; N,N′-caprolactam disulfide; and acombination thereof, wherein the at least one additionalsulfur-containing compound is present in the formulation in an amountfrom 0.1 phr to 20 phr, or from 1 phr to 10 phr, or from 1.0 phr to 7.0phr, or from 1.5 phr to 6.5 phr, or from 1.5 phr to 5.5 phr, or from 1.5phr to 5.0 phr, or from 2.0 phr to 6.0 phr, or from 2.0 phr to 5.5 phr,or from 2.0 phr to 5.0 phr, or from 2.0 phr to 4.5 phr, or from 2.5 phrto 5.0 phr, or from 2.5 phr to 4.5 phr, or from 3.0 phr to 6.0 phr, orfrom 3.0 phr to 5.5 phr, or from 3.0 phr to 5.0 phr.

According to particular embodiments, an elastomer composition of thepresent invention comprising, consisting essentially of, or consistingof at least one elastomer (either saturated, unsaturated, or both), atleast one organic peroxide and at least one sulfur-containing compound,wherein the elastomer composition does not include any bis-, tri- orhigher poly-maleimides, or bis-, tri- or higher poly-citraconimides,which has been cured in the full or partial presence of oxygen, has lesssurface tackiness in comparison to an elastomer composition that hasbeen cured according to an identical process and that has an identicalcomposition except that it includes one or more bis-, tri- or higherpoly-maleimides (e.g., HVA-2), or bis-, tri- or higherpoly-citraconimides. Surface tackiness may be judged, for example, bythe Facial Tissue Paper Test described herein.

Organic Peroxide Compositions Comprising Organophosphite Compounds

According to an embodiment of the present invention, an organic peroxideformulation comprises, consists essentially of, or consists of at leastone organic peroxide and at least one organophosphite compound. Theorganic peroxide(s) and organophosphite compound(s), and theirrespective amounts, are preferably selected such that the formulation iscapable of curing an elastomer composition in the full or partialpresence of oxygen (e.g., using a hot air oven or tunnel, or a steamautoclave). Embodiments of the formulations comprising organicperoxide(s) and organophosphite compound(s) are described in Example 5.

Non-limiting examples of organophosphite compounds that may be used informulations of the present invention include Irgafos® 168(tris(2,4-di-tert-butylphenyl) phosphite), TPP (triphenyl phosphite),phenyl didecyl phosphite, di-phenyl isodecyl phosphite, TNPP(tris-nonylphenyl phosphite), and 4,4′-isopropylidene diphenol alkyl(C12-C15) phosphite.

In one embodiment of the invention, the at least one organophosphitecompound comprises, consists essentially of, or consists of Irgafos® 168(tris(2,4-di-tert-butylphenyl) phosphite), TPP (triphenyl phosphite), ora combination thereof.

The ratio of the at least one organophosphite to the at least oneorganic peroxide is not particularly limited, but may be between about1:about 0.1 and about 1:about 10. For example, about 1:about 0.7, about1:about 1, about 1:about 1.5, about 1:about 3, about 1:about 3.6, orabout 1:about 7.

According to one embodiment, the organic peroxide formulation of thepresent invention comprises, consists essentially of, or consists of:

at least one organic peroxide (for example, in an amount from 20 wt % to99 wt %, or from 30 wt % to 95 wt % or from 40 wt % to 95 wt %, or from30 wt % to 90 wt %, or from 40 wt % to 90 wt %, or from 45 wt % to 90 wt%, or from 45 wt % to 85 wt %, or from 45 wt % to 80 wt %, or from 45 wt% to 75 wt %, or from 50 wt % to 95 wt %, or from 50 wt % to 90 wt %, orfrom 50 wt % to 80 wt %, or from 50 wt % to 75 wt %, from 60 wt % to 90wt %, based on the total organic peroxide formulation);

at least one organophosphite compound (for example, in an amount from 5wt % to 70 wt %, or 5 wt % to 60 wt %, or from 10 wt % to 60 wt %, orfrom 15 wt % to 60 wt %, or from 20 wt % to 60 wt %, or from 5 wt % to50 wt %, or from 10 wt % to 50 wt %, or from 10 wt % to 70 wt %, or from10 wt % to 40 wt %, based on the total organic peroxide formulation);and

at least one optional inert filler (for example, in an amount from 0.01wt % to 40 wt %, or from 0.01 wt % to 20 wt %, or from 0.01 wt % to 20wt %, or from 0.01 wt % to 10 wt %, or from 0.01 wt % to 5 wt %, or from0.01 wt % to 2 wt %, or from 0.01 wt % to 0.1 wt %, based on the totalorganic peroxide formulation),

wherein the at least one peroxide and the at least one organophosphitecompound, and their respective amounts, are selected such that theformulation is capable of curing an elastomer composition in the full orpartial presence of oxygen, and wherein the cured elastomer compositionis substantially or completely tack-free.

An additional embodiment of the present invention provides an elastomercomposition comprising, consisting essentially of, or consisting of:

at least one elastomer (either saturated, unsaturated, or both); and

at least one organic peroxide,

and at least one organophosphite compound,

wherein the elastomer composition is curable in the full or partialpresence of oxygen (e.g., using a hot air oven or tunnel, or a steamautoclave). Preferably, the cured elastomer composition is completely orsubstantially tack-free.

According to particular embodiments, the elastomer compositioncomprises, consists essentially of, or consists of at least oneelastomer (either saturated, unsaturated, or both); and

at least one organic peroxide in an amount from 0.1 phr to 20.0 phr, orfrom 0.1 phr to 15.0 phr, from 0.1 phr to 10.0 phr, or from 1.0 phr to20 phr, or from 1.0 phr to 15 phr, or from 1.0 phr to 10.0 phr (partsper hundred rubber), or from 2.0 phr to 20.0 phr, or from 2.0 phr to15.0 phr, or from 2.0 phr to 10.0 phr, or from 3.0 phr to 20.0 phr, orfrom 3.0 phr to 15.0 phr, or from 3.0 phr to 10.0 phr, or from 4.0 phrto 10.0 phr, or from 5.0 phr to 10.0 phr; and

at least one organophosphite compound (e.g.,tris(2,4-di-tert-butylphenyl) phosphite, triphenyl phosphite, or acombination thereof) in an amount from 0.1 phr to 20 phr, or from 0.1phr to 15 phr, or from 0.1 phr to 10 phr, or from 0.1 phr to 8 phr, from1 phr to 20 phr, or from 1 phr to 15 phr, or from 1 phr to 10 phr, orfrom 1 phr to 8 phr, or from 1 phr to 5 phr, or from 2.0 phr to 10.0phr, or from 2.0 phr to 8.0 phr, or from 2.0 phr to 6.0 phr, or from 3.0phr to 7.0 phr, or from 3.0 phr to 8.5 phr, or from 3.0 phr to 8.0 phr,or from 3.0 phr to 6.5 phr, or from 3.0 phr to 6.0 phr, or from 3.0 phrto 5.0 phr; and

optionally at least one additive selected from the group consisting ofprocess oils (e.g., aliphatic process oils), process aids, pigments,dyes, tackifiers, waxes, reinforcing aids, UV stabilization agents,blowing agents, scorch protectors, activators, antiozonants and coagents(e.g., those marketed by Sartomer).

According to particular embodiments, an elastomer composition of thepresent invention comprising, consisting essentially of, or consistingof at least one elastomer (either saturated, unsaturated, or both), atleast one organic peroxide and at least one organophosphite compound,which has been cured in the full or partial presence of oxygen, has lesssurface tackiness in comparison to an elastomer composition that hasbeen cured according to an identical process and that has an identicalcomposition except that it does not include any organophosphitecompounds.

Organic Peroxide Compositions Comprising HALS Compounds

According to an embodiment of the present invention, an organic peroxideformulation comprises, consists essentially of, or consists of at leastone organic peroxide and at least one HALS (Hindered Amine LightStabilizer) compound. As used herein, HALS compounds include2,2,6,6-tetramethyl piperidine and derivatives thereof, wherein the HALScompound may be a single compound, or may be polymeric in nature. Theorganic peroxide(s) and HALS compound(s), and their respective amounts,are preferably selected such that the formulation is capable of curingan elastomer composition in the full or partial presence of oxygen(e.g., using a hot air oven or tunnel, or a steam autoclave).Embodiments of the formulations comprising organic peroxide(s) and HALScompound(s) are described in Example 6.

Non-limiting examples of HALS compounds that may be used in formulationsof the present invention include Chimmasorb® 944(poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-s-triazine-2,4-diyl]-[2,2,6,6-tetramethyl-4-piperidyl)imino]-hexamethylene-[(2,2,6,6-tetramethyl-4-piperidyl)imino]],a HALS made by BASF); and Tinuvin® 770([bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate], a HALS made by BASF).

In one embodiment of the invention, the at least one HALS compoundcomprises, consists essentially of, or consists ofpoly[[6-[(1,1,3,3-tetramethylbutyl)amino]-s-triazine-2,4-diyl]-[(2,2,6,6-tetramethyl-4-piperidyl)imino]-hexamethylene-[(2,2,6,6-tetramethyl-4-piperidyl)imino]],bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate, or a combinationthereof.

The ratio of the at least one HALS compound to the at least one organicperoxide is not particularly limited, but may be between about 1:about0.1 and about 1:about 10; for example, about 1:about 0.7, about 1:about1, about 1:about 1.5, about 1:about 3, about 1:about 3.6, or about1:about 7.

According to a particular embodiment, the organic peroxide formulationof the present invention comprises, consists essentially of, or consistsof:

at least one organic peroxide (for example, in an amount from 20 wt % to99 wt %, or from 30 wt % to 95 wt % or from 40 wt % to 95 wt %, or from30 wt % to 90 wt %, or from 40 wt % to 90 wt %, or from 45 wt % to 90 wt%, or from 45 wt % to 85 wt %, or from 45 wt % to 80 wt %, or from 45 wt% to 75 wt %, or from 50 wt % to 95 wt %, or from 50 wt % to 90 wt %, orfrom 50 wt % to 80 wt %, or from 50 wt % to 75 wt %, from 60 wt % to 90wt %, based on the total organic peroxide formulation);

at least one HALS compound (for example, in an amount from 5 wt % to 70wt %, or 5 wt % to 60 wt %, or from 10 wt % to 60 wt %, or from 15 wt %to 60 wt %, or from 20 wt % to 60 wt %, or from 5 wt % to 50 wt %, orfrom 10 wt % to 50 wt %, or from 10 wt % to 70 wt %, or from 10 wt % to40 wt %, based on the total organic peroxide formulation); and

at least one optional inert filler (for example, in an amount from 0.01wt % to 40 wt %, or from 0.01 wt % to 20 wt %, or from 0.01 wt % to 20wt %, or from 0.01 wt % to 10 wt %, or from 0.01 wt % to 5 wt %, or from0.01 wt % to 2 wt %, or from 0.01 wt % to 0.1 wt %, based on the totalorganic peroxide formulation),

wherein the at least one peroxide and the at least one HALS compound,and their respective amounts, are selected such that the formulation iscapable of curing an elastomer composition in the full or partialpresence of oxygen, and wherein the cured elastomer composition issubstantially or completely tack-free.

An additional embodiment of the present invention provides an elastomercomposition comprising, consisting essentially of, or consisting of:

at least one elastomer (either saturated, unsaturated, or both); and

at least one organic peroxide,

and at least one HALS compound,

wherein the elastomer composition is curable in the full or partialpresence of oxygen (e.g., using a hot air oven or tunnel, or a steamautoclave). Preferably, the cured elastomer composition is completely orsubstantially tack-free.

According to particular embodiments, the elastomer compositioncomprises, consists essentially of, or consists of at least oneelastomer (either saturated, unsaturated, or both); and

at least one organic peroxide in an amount from 0.1 phr to 20.0 phr, orfrom 0.1 phr to 15.0 phr, from 0.1 phr to 10.0 phr, or from 1.0 phr to20 phr, or from 1.0 phr to 15 phr, or from 1.0 phr to 10.0 phr (partsper hundred rubber), or from 2.0 phr to 20.0 phr, or from 2.0 phr to15.0 phr, or from 2.0 phr to 10.0 phr, or from 3.0 phr to 20.0 phr, orfrom 3.0 phr to 15.0 phr, or from 3.0 phr to 10.0 phr, or from 4.0 phrto 10.0 phr, or from 5.0 phr to 10.0 phr;

at least one HALS compound (e.g.,poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-s-triazine-2,4-diyl]-[2,2,6,6-tetramethyl-4-piperidyl)imino]-hexamethylene-[(2,2,6,6-tetramethyl-4-piperidyl)imino]],bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate, or a combinationthereof) in an amount from 0.1 phr to 20 phr, or from 0.1 phr to 15 phr,or from 0.1 phr to 10 phr, or from 0.1 phr to 8 phr, from 1 phr to 20phr, or from 1 phr to 15 phr, or from 1 phr to 10 phr, or from 1 phr to8 phr, or from 1 phr to 5 phr, or from 2.0 phr to 10.0 phr, or from 2.0phr to 8.0 phr, or from 2.0 phr to 6.0 phr, or from 3.0 phr to 7.0 phr,or from 3.0 phr to 8.5 phr, or from 3.0 phr to 8.0 phr, or from 3.0 phrto 6.5 phr, or from 3.0 phr to 6.0 phr, or from 3.0 phr to 5.0 phr; and

optionally at least one additive selected from the group consisting ofprocess oils (e.g., aliphatic process oils), process aids, pigments,dyes, tackifiers, waxes, reinforcing aids, UV stabilization agents,blowing agents, scorch protectors, activators, antiozonants and coagents(e.g., those marketed by Sartomer).

According to particular embodiments, an elastomer composition of thepresent invention comprising, consisting essentially of, or consistingof at least one elastomer (either saturated, unsaturated, or both), atleast one organic peroxide, and at least one HALS compound, which hasbeen cured in the full or partial presence of oxygen, has less surfacetackiness in comparison to an elastomer composition that has been curedaccording to an identical process and that has an identical compositionexcept that it does not include any HALS compounds.

Organic Peroxide Compositions Comprising Aliphatic Allyl UrethaneCompounds

According to an embodiment of the present invention, an organic peroxideformulation comprises, consists essentially of, or consists of at leastone organic peroxide and at least one aliphatic allyl urethane compound.As used herein, an aliphatic allyl urethane compound contains at leastone allylic group functionality and at least one urethane groupfunctionality. The organic peroxide(s) and aliphatic allyl urethanecompound(s), and their respective amounts, are preferably selected suchthat the formulation is capable of curing an elastomer composition inthe full or partial presence of oxygen (e.g., using a hot air oven ortunnel, or a steam autoclave). Embodiments of the formulationscomprising organic peroxide(s) and aliphatic allyl urethane compound(s)are described in Example 7.

An example of an aliphatic allyl urethane compound that may be used informulations of the present invention includes CN9102®, available fromSartomer.

The ratio of the at least one aliphatic allyl urethane compound to theat least one organic peroxide is not particularly limited, but may bebetween about 1:about 0.1 and about 1:about 10; for example, about1:about 0.24, about 1:about 0.40, about 1:about 0.54, about 1:about 0.8,about 1:about 0.9, about 1:about 1, about 1:about 1.8, about 1:about2.4, about 1:about 3.2, about 1:about 7.2, or about 1:about 9.6.

According to one of the particular embodiments, the organic peroxideformulation of the present invention comprises, consists essentially of,or consists of:

at least one organic peroxide (for example, in an amount from 20 wt % to99 wt %, or from 30 wt % to 95 wt % or from 40 wt % to 95 wt %, or from30 wt % to 90 wt %, or from 40 wt % to 90 wt %, or from 45 wt % to 90 wt%, or from 45 wt % to 85 wt %, or from 45 wt % to 80 wt %, or from 45 wt% to 75 wt %, or from 50 wt % to 95 wt %, or from 50 wt % to 90 wt %, orfrom 50 wt % to 80 wt %, or from 50 wt % to 75 wt %, from 60 wt % to 90wt %, based on the total organic peroxide formulation);

at least one aliphatic allyl urethane compound (for example, in anamount from 5 wt % to 80 wt %, or 5 wt % to 70 wt %, or 5 wt % to 65 wt%, or from 10 wt % to 80 wt %, or 10 wt % to 70 wt %, or 10 wt % to 65wt %, or from 15 wt % to 80 wt %, or 15 wt % to 70 wt %, or 15 wt % to65 wt %, or from 20 wt % to 80 wt %, or 20 wt % to 70 wt %, or 20 wt %to 65 wt %, or from 30 wt % to 80 wt %, or from 30 wt % to 70 wt %, orfrom 30 wt % to 65 wt %, or from 30 wt % to 60 wt %, based on the totalorganic peroxide formulation); and

at least one optional inert filler (for example, in an amount from 0.01wt % to 40 wt %, or from 0.01 wt % to 20 wt %, or from 0.01 wt % to 20wt %, or from 0.01 wt % to 10 wt %, or from 0.01 wt % to 5 wt %, or from0.01 wt % to 2 wt %, or from 0.01 wt % to 0.1 wt %, based on the totalorganic peroxide formulation),

wherein the at least one peroxide and the at least one aliphatic allylurethane compound, and their respective amounts, are selected such thatthe formulation is capable of curing an elastomer composition in thefull or partial presence of oxygen, and wherein the cured elastomercomposition is substantially or completely tack-free.

An additional embodiment of the present invention provides an elastomercomposition comprising, consisting essentially of, or consisting of:

at least one elastomer (either saturated, unsaturated, or both); and

at least one organic peroxide,

and at least one aliphatic allyl urethane compound,

wherein the elastomer composition is curable in the full or partialpresence of oxygen (e.g., using a hot air oven or tunnel, or a steamautoclave). Preferably, the cured elastomer composition is completely orsubstantially tack-free.

According to particular embodiments, the elastomer compositioncomprises, consists essentially of, or consists of at least oneelastomer (either saturated, unsaturated, or both); and

at least one organic peroxide in an amount from 0.1 phr to 20.0 phr, orfrom 0.1 phr to 15.0 phr, from 0.1 phr to 10.0 phr, or from 1.0 phr to20 phr, or from 1.0 phr to 15 phr, or from 1.0 phr to 10.0 phr (partsper hundred rubber), or from 2.0 phr to 20.0 phr, or from 2.0 phr to15.0 phr, or from 2.0 phr to 10.0 phr, or from 3.0 phr to 20.0 phr, orfrom 3.0 phr to 15.0 phr, or from 3.0 phr to 10.0 phr, or from 4.0 phrto 10.0 phr, or from 5.0 phr to 10.0 phr; or from 5.0 phr to 8.0 phr;

at least one aliphatic allyl urethane compound in an amount from 0.1 phrto 20 phr, or from 0.1 phr to 15 phr, or from 0.1 phr to 10 phr, or from0.1 phr to 8 phr, from 1 phr to 20 phr, or from 1 phr to 15 phr, or from1 phr to 10 phr, or from 1 phr to 8 phr, or from 1 phr to 5 phr, or from2.0 phr to 10.0 phr, or from 2.0 phr to 8.0 phr, or from 2.0 phr to 6.0phr, or from 3.0 phr to 10.0 phr, or from 3.0 phr to 7.0 phr, or from3.0 phr to 8.5 phr, or from 3.0 phr to 8.0 phr, or from 3.0 phr to 6.5phr, or from 3.0 phr to 6.0 phr, or from 3.0 phr to 5.0 phr; and

optionally at least one additive selected from the group consisting ofprocess oils (e.g., aliphatic process oils), process aids, pigments,dyes, tackifiers, waxes, reinforcing aids, UV stabilization agents,blowing agents, scorch protectors, activators, antiozonants and coagents(e.g., those marketed by Sartomer).

According to particular embodiments, an elastomer composition of thepresent invention comprising, consisting essentially of, or consistingof at least one elastomer (either saturated, unsaturated, or both), atleast one organic peroxide and at least one aliphatic allyl urethanecompound, which has been cured in the full or partial presence ofoxygen, has less surface tackiness in comparison to an elastomercomposition that has been cured according to an identical process andthat has an identical composition except that it does not include anyaliphatic allyl urethane compounds.

Organic Peroxide Compositions Comprising Nitroxide(s) and Quinone(s)

According to an embodiment of the present invention, an organic peroxideformulation comprises, consists essentially of, or consists of at leastone organic peroxide, at least one sulfur-containing compound, at leastone nitroxide-containing compound (e.g., 4-hydroxy-TEMPO (4-OHT)) and atleast one quinone-containing compound (preferablymono-tert-butylhydroquinone or MTBHQ). The organic peroxide(s),nitroxide-containing compound(s), quinone-containing compound(s),sulfur-containing compound(s), and their respective amounts, arepreferably selected such that the formulation is capable of curing anelastomer composition in the full or partial presence of oxygen (e.g.,using a hot air oven or tunnel, or a steam autoclave). Embodiments ofthe formulations comprising organic peroxide(s), nitroxide-containingcompound(s), quinone-containing compound(s), and sulfur-containingcompound(s) are described in Example 9.

Examples of the nitroxide (or “nitroxide-containing compound”) mayinclude derivatives of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl),such as 4-hydroxy TEMPO (4-OHT) and 4-acetamido TEMPO. As used herein,the terms “quinone” or “quinone-containing compound” include bothquinones and hydroquinones as well as ethers thereof such as monoalkyl,monoaryl, monoaralkyl and bis(hydroxyalkyl) ethers of hydroquinones.Non-limiting examples of quinones that may be used in formulations ofthe present invention include mono-tert-butylhydroquinone (MTBHQ),hydroquinone, hydroquinone mono-methyl ether (HQMME) (also known as4-methoxy phenol), mono-t-amylhydroquinone, hydroquinonebis(2-hydroxyethyl) ether, 4-ethoxy phenol, 4-phenoxy phenol,4-(benzyloxy) phenol, 2,5-bis (morpholinomethyl) hydroquinone, andbenzoquinone.

Non-limiting examples of sulfur-containing compound(s) that may be usedin combination with the nitroxide(s) and quinone(s) in the organicperoxide formulations include benzothiazyl disulfide,poly(alkylphenol)polysulfide, N,N′-caprolactam disulfide, and4,4′-dithiomorpholine.

The ratio of nitroxide (e.g., 4-OHT):quinone (e.g., MTBHQ) is notparticularly limited, but is preferably about 1:about 1. Other preferredratios of nitroxide (e.g., 4-OHT):quinone (e.g., MTBHQ) include, but arenot limited to, about 1:about 0.5; about 0.5:about 1.0, about 1:about0.25; and about 0.25:about 1.0.

According to one particular embodiment, the organic peroxide formulationof the present invention comprises, consists essentially of, or consistsof:

at least one organic peroxide (for example, in an amount from 20 wt % to99 wt %, or from 30 wt % to 95 wt % or from 40 wt % to 95 wt %, or from30 wt % to 90 wt %, or from 40 wt % to 90 wt %, or from 45 wt % to 90 wt%, or from 45 wt % to 85 wt %, or from 45 wt % to 80 wt %, or from 45 wt% to 75 wt %, or from 50 wt % to 95 wt %, or from 50 wt % to 90 wt %, orfrom 50 wt % to 80 wt %, or from 50 wt % to 75 wt %, from 60 wt % to 90wt %, based on the total organic peroxide formulation);

at least one nitroxide-containing compound (e.g., 4-OHT) and at leastone quinone-containing compound (e.g., MTBHQ); for example, each of thenitroxide-containing compound(s) and the quinone-containing compound(s)may be provided in an amount from 0.01 wt % to 5 wt %, or 0.01 wt % to2.5 wt %, or from 0.01 wt % to 1 wt %, or from 0.01 wt % to 0.5 wt %, orfrom 0.01 wt % to 0.25 wt %, or from 0.01 wt % to 0.15 wt %, based onthe total organic peroxide formulation), wherein thenitroxide-containing compound(s) (e.g., 4-OHT) and quinone-containingcompound(s) (e.g., MTBHQ) are preferably provided in a ratio of about1:about 1, or alternatively about 1:about 0.5, or about 0.5:about 1.0,or about 1:about 0.25; or about 0.25:about 1.0;

at least one sulfur-containing compound (for example, in an amount from5 wt % to 50 wt %, or from 10 wt % to 50 wt %, or from 15 wt % to 45 wt%, or from 20 wt % to 70 wt %, or from 20 wt % to 65 wt %, or from 20 wt% to 60 wt %, or from 25 wt % to 70 wt %, or from 25 wt % to 65 wt %, orfrom 25 wt % to 60 wt %, or from 30 wt % to 70 wt %, or from 30 wt % to65 wt %, or from 30 wt % to 60 wt %, or from 35 wt % to 70 wt %, or from35 wt % to 65 wt %, or from 35 wt % to 60 wt %, or from 40 wt % to 70 wt%, or from 40 wt % to 65 wt %, or from 40 wt % to 60 wt %, or from 40 wt% to 55 wt %, or from 40 wt % to 50 wt %, based on the total organicperoxide formulation); and

at least one optional inert filler (for example, in an amount from 0.01wt % to 40 wt %, or from 0.01 wt % to 20 wt %, or from 0.01 wt % to 20wt %, or from 0.01 wt % to 10 wt %, or from 0.01 wt % to 5 wt %, or from0.01 wt % to 2 wt %, or from 0.01 wt % to 0.1 wt %, based on the totalorganic peroxide formulation),

wherein the at least one peroxide, 4-OHT, MTBHQ, at least onesulfur-containing compound, and their respective amounts, are selectedsuch that the formulation is capable of curing an elastomer compositionin the full or partial presence of oxygen, and wherein the curedelastomer composition is substantially or completely tack-free.

An additional embodiment of the present invention provides an elastomercomposition comprising, consisting essentially of, or consisting of:

at least one elastomer (either saturated, unsaturated, or both),

at least one organic peroxide,

at least one nitroxide-containing compound (e.g., 4-OHT),

at least one quinone-containing compound (e.g., MTBHQ), and

at least one sulfur-containing compound (e.g., benzothiazyl disulfide,poly(alkylphenol)polysulfide, N,N′-caprolactam disulfide, and/or4,4′-dithiomorpholine),

wherein the elastomer composition is curable in the full or partialpresence of oxygen (e.g., using a hot air oven or tunnel, or a steamautoclave). Preferably, the cured elastomer composition is completely orsubstantially tack-free.

According to particular embodiments, the elastomer compositioncomprises, consists essentially of, or consists of at least oneelastomer (either saturated, unsaturated, or both); and

at least one organic peroxide in an amount from 0.1 phr to 20.0 phr, orfrom 0.1 phr to 15.0 phr, from 0.1 phr to 10.0 phr, or from 1.0 phr to20 phr, or from 1.0 phr to 15 phr, or from 1.0 phr to 10.0 phr (partsper hundred rubber), or from 2.0 phr to 20.0 phr, or from 2.0 phr to15.0 phr, or from 2.0 phr to 10.0 phr, or from 3.0 phr to 20.0 phr, orfrom 3.0 phr to 15.0 phr, or from 3.0 phr to 10.0 phr, or from 3.0 phrto 8.0 phr, or from 3.0 phr to 6.0 phr, or from 4.0 phr to 10.0 phr, orfrom 4.0 phr to 8.0 phr, or from 4.0 phr to 6.0 phr;

at least one nitroxide (e.g., 4-OHT) and at least one quinone (e.g.,MTBHQ), each in an amount from 0.01 phr to 5 phr, or from 0.01 phr to 3phr, or from 0.01 phr to 1 phr, or from 0.01 phr to 0.75 phr, or from0.1 phr to 3 phr, or from 0.1 phr to 1 phr, or from 0.1 phr to 5 phr;

at least one sulfur-containing compound in an amount from 0.1 phr to 20phr, or from 0.1 phr to 10 phr, or from 0.1 phr to 7.5 phr, or from 0.1phr to 5 phr, or from 0.1 phr to 2.5 phr, or from 1 phr to 20 phr, orfrom 1 phr to 10 phr, or from 1 phr to 7.5 phr, or from 1 phr to 5 phr,or from 1 phr to 2.5 phr; and

optionally at least one additive selected from the group consisting ofprocess oils (e.g., aliphatic process oils), process aids, pigments,dyes, tackifiers, waxes, reinforcing aids, UV stabilization agents,blowing agents, scorch protectors, activators, antiozonants and coagents(e.g., those marketed by Sartomer).

Additional Organic Peroxide Compositions

According to additional embodiments of the present invention, one ormore of the compounds described herein that are blended with organicperoxide(s) to produce peroxide formulations of the present invention(e.g., sulfur-containing compounds, organophosphite compounds, HALScompounds, aliphatic allyl urethane compounds, nitroxides, and quinones)may be combined together in the same organic peroxide formulation.

In addition to sulfur-containing compounds, organophosphite compounds,HALS compounds, aliphatic allyl urethane compounds, nitroxides, andquinones, additional compounds that may be blended with at least oneorganic peroxide to produce peroxide formulations of the presentinvention include drying oils and cellulose compounds.

Drying oils may include oils derived from plant, animal, and fishsources including, for example, glycerol triesters of fatty acids whichare characterized by relatively high levels of polyunsaturated fattyacids, especially eleostearic acid and alpha-linolenic acid. Accordingto particular embodiments, the at least one drying oil is selected fromthe group consisting of: tung oil, hemp oil, biofene ortrans-beta-farnesene (made by Amyris), linseed oil, poppy oil, walnutoil, sunflower oil, cottonseed oil, corn oil, soybean oil, sardine oil,herring oil, safflower oil, flax seed oil, perilla oil, and acombination thereof. According to preferred embodiments, the drying oilis tung oil or hemp oil.

Non-limiting examples of cellulose compounds suitable for use in thepresent invention include cellulose and its derivatives, includingcellulose esters, cellulose ethers and combinations thereof; forexample, cellulose acetate butyrate (CAB), cellulose acetateproprionate, cellulose acetate, cellulose, micronized cellulose,cellulose gum, microcrystalline cellulose, carboxymethyl cellulose,hydroxypropyl cellulose (HPC), hydroxypropylmethyl cellulose (HMPC),hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, celluloseacetate phthalate, ethyl hydroxyethyl cellulose, hydroxyethyl methylcellulose, ethyl methyl cellulose, and combinations thereof. Accordingto preferred embodiments, the cellulose compound is cellulose acetatebutyrate (CAB).

In accordance with particular embodiments, an organic peroxideformulation comprises, consists essentially of, or consists of at leastone organic peroxide and one or more compounds selected from the groupconsisting of: sulfur-containing compounds, organophosphite compounds,HALS compounds, aliphatic allyl urethane compounds, nitroxide-containingcompounds (e.g., 4-OHT), quinone-containing compounds (e.g., MTBHQ),drying oils, cellulose compounds and a combination thereof. Optionaladditive(s) that may be included in the formulation are selected fromthe group consisting of process oils (e.g., aliphatic process oils),process aids, pigments, dyes, tackifiers, waxes, reinforcing aids, UVstabilization agents, blowing agents, scorch protectors, activators,antiozonants and coagents (e.g., those marketed by Sartomer). Thecomponents of the formulation and their respective amounts, are selectedsuch that the formulation is capable of curing an elastomer compositionin the full or partial presence of oxygen (e.g., using a hot air oven ortunnel, or a steam autoclave).

According to another embodiment, an organic peroxide formulationcomprises, consists essentially of, or consists of at least one organicperoxide, at least one sulfur-containing compound, optionally at leastone nitroxide-containing compound, optionally at least onequinone-containing compound, and one or more compounds selected from thegroup consisting of: organophosphite compounds, HALS compounds,aliphatic allyl urethane compounds, drying oils, cellulose compounds anda combination thereof. Optional additive(s) that may be included in theformulation are selected from the group consisting of process oils(e.g., aliphatic process oils), process aids, pigments, dyes,tackifiers, waxes, reinforcing aids, UV stabilization agents, blowingagents, scorch protectors, activators, antiozonants and coagents (e.g.,those marketed by Sartomer). According to certain embodiments, theformulation does not include any bis-, tri- or higher poly-maleimides,or bis-, tri- or higher poly-citraconimides type coagents. Thecomponents of the formulation and their respective amounts, are selectedsuch that the formulation is capable of curing an elastomer compositionin the full or partial presence of oxygen (e.g., using a hot air oven ortunnel, or a steam autoclave).

According to another embodiment, an organic peroxide formulationcomprises, consists essentially of, or consists of at least one organicperoxide, at least one nitroxide-containing compound (e.g., 4-OHT), atleast one quinone-containing compound (e.g., MTBHQ), and one or morecompounds selected from the group consisting of: sulfur-containingcompounds, organophosphite compounds, HALS compounds, aliphatic allylurethane compounds, drying oils, cellulose compounds and a combinationthereof. Optional additive(s) that may be included in the formulationare selected from the group consisting of process oils (e.g., aliphaticprocess oils), process aids, pigments, dyes, tackifiers, waxes,reinforcing aids, UV stabilization agents, blowing agents, scorchprotectors, activators, antiozonants and coagents (e.g., those marketedby Sartomer). The components of the formulations and their respectiveamounts, are selected such that the formulation is capable of curing anelastomer composition in the full or partial presence of oxygen (e.g.,using a hot air oven or tunnel, or a steam autoclave).

According to another embodiment, an elastomer composition comprises,consists essentially of, or consists of at least one elastomer, at leastone peroxide, and one or more compounds selected from the groupconsisting of: sulfur-containing compounds, organophosphite compounds,HALS compounds, aliphatic allyl urethane compounds, nitroxide-containingcompounds (e.g., 4-OHT), quinone-containing compounds (e.g., MTBHQ),drying oils, cellulose compounds and a combination thereof, wherein theelastomer composition is curable in the full or partial presence ofoxygen.

According to another embodiment, an elastomer composition comprises,consists essentially of, or consists of at least one elastomer, at leastone organic peroxide, at least one sulfur-containing compound,optionally at least one nitroxide-containing compound, optionally atleast one quinone-containing compound, and one or more compoundsselected from the group consisting of: organophosphite compounds, HALScompounds, aliphatic allyl urethane compounds, drying oils, cellulosecompounds and a combination thereof, wherein the elastomer compositionis curable in the full or partial presence of oxygen.

According to another embodiment, an elastomer composition comprises,consists essentially of, or consists of at least one elastomer, at leastone peroxide, at least one nitroxide-containing compound (e.g., 4-OHT),at least one quinone-containing compound (e.g., MTBHQ), and one or morecompounds selected from the group consisting of: sulfur-containingcompounds, organophosphite compounds, HALS compounds, aliphatic allylurethane compounds, drying oils, cellulose compounds and a combinationthereof, wherein the elastomer composition is curable in the full orpartial presence of oxygen.

Elastomers Suitable for Use in Embodiments of the Present Invention

In at least one embodiment, the elastomer compositions of the presentinvention may comprise a saturated elastomer, an unsaturated elastomer,or a blend of both a saturated and unsaturated elastomer.

According to particular embodiments, the elastomer compositions of thepresent invention further comprise at least one polymer. The at leastone polymer of the elastomer composition may comprise a saturatedpolymer, an unsaturated polymer, or both a saturated and unsaturatedpolymer.

It should be noted that commercially-available pre-compounded elastomersmay be used in accordance with the present invention. These elastomersmay contain additives such as carbon black filler, process oils, moldrelease agents, antioxidants and/or heat stabilizers. According toparticular embodiments, the at least one elastomer is part of anelastomer masterbatch that includes one or more of these additives. Forexample, an elastomer masterbatch may comprise, consist essentially of,or consist of the at least one elastomer and one or more additivesselected from the group consisting of carbon black, polyethylene glycol,at least one process oil (e.g., liquid saturated hydrocarbons, such asPrimol® 352), at least one antioxidant (e.g.,2,2,4-trimethyl-1,2-dihydroquinoline, CAS#26780-96-1 also referred to asStanguard® TMQ Powder), at least one mold release agent, at least oneheat stabilizer, and a combination thereof.

As used herein, the term “polymer” means a non-elastomeric polymercomprised of at least at least one monomer in polymerized form. The term“polymer” encompasses homopolymers and copolymers, where the term“copolymers” refers to a polymer comprised of at least two differentmonomers in polymerized form. For example, a copolymer in accordancewith the present disclosure may be a polymer comprising two differentmonomers, a terpolymer is a polymer comprising three different monomersor more.

In at least one embodiment, the polymer of the elastomer compositioncomprises a copolymer. The embodiments disclosed herein recite elastomercompositions comprising a copolymer. However, as one of ordinary skillin the art would readily appreciate, a homopolymer may be substituted inany embodiment comprising a copolymer, unless expressly indicated to thecontrary.

In at least one embodiment, the elastomer composition comprises at leastone elastomer and at least one copolymer. The elastomer and copolymermay be present in the elastomer composition at weight ratios rangingfrom 99:1 to 1:99, such as, for example, from 85:15 to 15:85, or from75:25 to 25:75. In at least one embodiment, the elastomer and copolymerare present in the elastomer composition in a 50:50 weight ratio. Inanother embodiment, the elastomer composition includes 100% elastomer(s)and no copolymer(s).

According to at least one embodiment, the elastomer compositioncomprises at least one saturated elastomer. The saturated elastomer canbe selected from, for example, silicon rubber without unsaturation (Q),methyl-polysiloxane (MQ), phenyl-methyl-polysiloxane (PMQ),poly(ethylene-vinyl acetate) (EVA), high-density polyethylene (HDPE),low-density polyethylene (LDPE), chlorinated poly(ethylene) (CM or CPE),poly(ethylene-propylene) (EPM), fluoroelastomers (FKM, FFKM) (e.g.,Viton® and Dyneon®), and combinations thereof.

According to at least one embodiment, the elastomer compositioncomprises at least one unsaturated elastomer. Unsaturated elastomersthat may be used in the elastomer composition include, for example,ethylene-propylene-diene terpolymer (EPDM), vinyl silicone rubber (VMQ),fluorosilicone (FVMQ), nitrile rubber (NBR),acrylonitrile-butadiene-styrene (ABS), styrene butadiene rubber (SBR),styrene-butadiene-styrene block copolymers (SBS), polybutadiene rubber(BR), styrene-isoprene-styrene block copolymers (SIS), partiallyhydrogenated acrylonitrile butadiene (HNBR), natural rubber (NR),synthetic polyisoprene rubber (IR), neoprene rubber (CR),polychloropropene, bromobutyl rubber (BIIR), chlorobutyl rubber, andcombinations thereof.

According to particular embodiments, the elastomers of the presentinvention do not include fluorine-containing elastomers, and do notinclude elastomers that contain iodine or bromine.

In accordance with at least one embodiment, the elastomer compositioncomprises at least one saturated copolymer. Non-limiting examples ofsaturated polymers that may be used include copolymers of ethylene withpropylene, butylene, pentene, hexene, heptene, octene, and vinylacetate, such as, linear low density polyethylene (LLDPE), low densitypolyethylene (LDPE), high density polyethylene (HDPE),poly(ethylene-vinyl acetate) (EVA), poly(ethylene-propylene) (EPM),poly(ethylene-α-olefins) poly(ethylene-octene) (e.g., Engage®),poly(ethylene-hexene), poly(ethylene butylene) (e.g., Tafmer®),poly(ethylene-heptene), Vamac® polymers (e.g., poly(ethylene methylacrylate), poly(ethylene acrylate), and combinations with acrylic acid),and combinations thereof.

Additional non-limiting examples of elastomers and polymers suitable foruse in the current invention include polyurethane (AU and EU),vinylidene fluoride copolymers (CFM), silicone rubber, chlorosulfonatedpolyethylene (CSM), 5-vinyl-2-norbornene-EPDM (e.g. Keltan® ACE EPDM),and polysulfide rubber.

When a foamed product is desired, the elastomer composition may comprisea blowing agent.

According to particular embodiments, the elastomer compositions andorganic peroxide formulations of the present invention do not includeany organosiloxane gums, such as those described in U.S. Pat. No.4,376,184. According to further embodiments, the elastomer compositionsand organic peroxide formulations of the present invention do notinclude any polymer additives having a low molecular weight between1,000 and 15,000, such as those described in EP 0246745. According tofurther embodiments, the elastomer compositions and organic peroxideformulations of the present invention do not include any zinc oxide.

Embodiments of Methods of the Present Invention

At least one embodiment of the present invention relates to a method formanufacturing an article comprising an elastomer composition asdescribed herein, wherein the method comprises curing the elastomercomposition in the full or partial presence of oxygen (e.g., using a hotair oven or tunnel, or a steam autoclave).

As used herein, the term “curing” refers to the crosslinking of apolymer to form a strengthened or hardened polymer. A curing step may beperformed in any conventional manner, such as, for example, hot air,steam, or hot molding.

The method may comprise extruding an elastomer composition, as describedherein, to form an uncured preform article, and curing the uncuredpreform article. The elastomer composition may be extruded in thepresence of hot air to form the uncured preform. In at least oneembodiment, the preform is cured using microwaves or a steam autoclave.In at least one other embodiment, the preform is cured without usingmicrowaves or a steam autoclave.

In at least one embodiment, the extruded profile is heated in amicrowave zone in the presence of air directly from the extruder, thenpassed through a longer heated air tunnel to complete the cure of theelastomeric profile.

The method for manufacturing the article may be performed in a hot airtunnel, or any other known apparatus.

In at least one embodiment, the method for manufacturing the article canbe formed continuously. Continuous manufacturing may allow for theproduction of a continuous article, such as a continuous seal, asopposed to seals that must be pieced together from smaller parts.

At least one embodiment of the present disclosure relates to a methodfor manufacturing hose. The method may comprise extruding a length ofhose from an elastomer composition without curing the length of hose.The length of uncured hose may be collected and then cured, such as byexposing the uncured hose to steam.

At least one embodiment of the present invention relates to a processfor curing an elastomer composition, the process comprising curing theelastomer composition in the presence of oxygen, wherein the compositioncomprises, consists essentially of, or consists of:

at least one elastomer,

at least one organic peroxide, and

at least one sulfur-containing compound, wherein the elastomercomposition does not include any bis-, tri- or higher poly-maleimides,or bis-, tri- or higher poly-citraconimides. The process may furthercomprise mixing the at least one elastomer, the organic peroxide(s), andthe sulfur-containing compound(s), separately or together, and in anyorder, to provide the elastomer composition.

At least one embodiment of the present invention relates to a processfor curing an elastomer composition, the process comprising curing theelastomer composition in the presence of oxygen, wherein the mixturecomprises, consists essentially of, or consists of:

at least one elastomer,

at least one organic peroxide, and

at least one organophosphite compound. The process may further comprisemixing the at least one elastomer, the organic peroxide(s), and theorganophosphite compound(s), separately or together, and in any order,to provide the elastomer composition.

At least one embodiment of the present invention relates to a processfor curing an elastomer composition, the process comprising curing theelastomer composition in the presence of oxygen, wherein the mixturecomprises, consists essentially of, or consists of:

at least one elastomer,

at least one organic peroxide, and

at least one HALS compound. The process may further comprise mixing theat least one elastomer, the organic peroxide(s), and the HALScompound(s), separately or together, and in any order, to provide theelastomer composition.

At least one embodiment of the present invention relates to a processfor curing an elastomer composition, the process comprising curing theelastomer composition in the presence of oxygen, wherein the mixturecomprises, consists essentially of, or consists of:

at least one elastomer,

at least one organic peroxide, and

at least one aliphatic allyl urethane compound. The process may furthercomprise mixing the at least one elastomer, the organic peroxide(s), andthe aliphatic allyl urethane compound(s), separately or together, and inany order, to provide the elastomer composition.

At least one embodiment of the present invention relates to a processfor curing an elastomer composition, the process comprising curing theelastomer composition in the presence of oxygen, wherein the mixturecomprises, consists essentially of, or consists of:

at least one elastomer,

at least one organic peroxide,

at least one nitroxide-containing compound (e.g., 4-OHT),

at least one quinone-containing compound (e.g., MBTHQ), and

at least one sulfur-containing compound. The process may furthercomprise mixing the at least one elastomer, the organic peroxide(s), thenitroxide-containing compound(s), the quinone-containing compound(s),and the sulfur-containing compound(s) separately or together, and in anyorder, to provide the elastomer composition.

At least one embodiment of the present invention relates to a processfor curing an elastomer composition, the process comprising curing theelastomer composition in the presence of oxygen, wherein the mixturecomprises, consists essentially of, or consists of:

at least one elastomer,

at least one organic peroxide,

at least one optional sulfur-containing compound,

at least one optional nitroxide-containing compound (e.g., 4-OHT),

at least one optional quinone-containing compound (e.g., MBTHQ), and

one or more compounds selected from the group consisting of:organophosphite compounds, HALS compounds, aliphatic allyl urethanecompounds, drying oils, cellulose compounds and a combination thereof.The process may further comprise mixing the components separately ortogether, and in any order, to provide the elastomer composition.

In at least one embodiment, one or more conventional additives such asantioxidants (e.g., hindered phenols and polymeric quinolinederivatives), aliphatic process oils, process aids, pigments, dyes,tackifiers, waxes, reinforcing aids, UV stabilization agents, blowingagents, scorch protectors, activators, antiozonants or coagents may alsobe added to any of the elastomer compositions described herein before,after and/or during the curing step.

Embodiments of Elastomeric Articles of the Present Invention

Embodiments of the present invention also provide an elastomeric articlecomprising a cured elastomer composition as described herein.Preferably, the elastomeric article is completely or substantiallytack-free.

According to particular embodiments, the elastomeric article is anon-coating type (i.e., not a liquid coating).

Embodiments of the present invention may also include the process ofdissolving high molecular weight solid polymers in a solvent, thenremoving the solvent to create a solid elastomer structure which is thenhot air cured in a separate step (e.g., to provide a means to impregnatetextiles). One example of this commercial use is the production ofautomotive air bags. Additional examples include cured-in-place solidelastomer automotive and truck head gaskets, in which case a liquidsolution of solvent and a high molecular weight polymer, or blends ofpolymers, along with curatives, is applied to a metal surface. Thesolvent is removed, leaving a solid high molecular weight polymer ofcomplex structure on the metal part. This solid rubber gasket on themetal part can then be heated to crosslink the polymer. In each case,the solvent must be substantially or preferably completely removed fromthe solid polymer or elastomer; once the solid elastomer is free ofsolvent, the part can then be cured by applying heat to begin thecrosslinking reaction. This is in contrast to paints, coatings andvarnishes, wherein the cure process is concurrent with the solventremoval.

In at least one embodiment, an article of the present invention maycomprise a seal, hose, or gasket. Exemplary elastomeric articles thatmay be made in accordance with the compositions and methods of thepresent invention include O-rings, gaskets, diaphragms, seals, grommets,electrical insulators, shoe soles, septums, fittings, shrouds, sheets,belts, tubes, etc. The present disclosure also relates to automotive,industrial, or residential seals manufactured according to thecompositions and methods disclosed herein.

An additional benefit of the present invention is that mold-fouling isreduced during the manufacture of elastomer articles. In prior methods,oxygen present in a mold would prevent the complete reaction of theelastomer, which resulted in a residue of uncured elastomer that wouldbuild up in the mold. This build-up needed to be cleaned outperiodically.

According to additional embodiments, a method for reducing mold-foulingin the presence of oxygen comprises supplying an uncured elastomercomposition to a mold, wherein the uncured elastomer compositioncomprises, consists essentially of, or consists of at least oneelastomer (either saturated, unsaturated, or both) and an organicperoxide formulation as described herein.

The embodiments described herein are intended to be exemplary of theinvention and not limitations thereof. One skilled in the art willappreciate that modifications to the embodiments and examples of thepresent disclosure may be made without departing the scope of thepresent disclosure. The embodiments of the invention are described aboveusing the term “comprising” and variations thereof. However, it is theintent of the inventors that the term “comprising” may be substituted inany of the embodiments described herein with “consisting of” and“consisting essentially of” without departing the scope of theinvention.

The following examples further illustrate the best mode contemplated bythe inventors for the practice of their invention and are to beconstrued as illustrative and not in limitation thereof.

Abbreviations Used for the RPA Rheometer Test

ML (dN-m) is the minimum torque in deci-Newton-meters in a RPA rheometertest and relates to the viscosity of the elastomer composition at thetest temperature.

MH (dN-m) is the maximum torque in deci-Newton-meters in a RPA rheometertest and relates to the maximum amount of crosslinking attained.

MH−ML (dN-m) is the relative degree of crosslinking indeci-Newton-meters

Ts1 (min) is the time to attain a 1 dN-m increase from the minimumtorque in minutes

Ts2 (min) is the time to attain a 2 dN-m increase from the minimumtorque in minutes

Tc50 (min) is the time to attain 50% of the MH−ML (dN-m) cure state inminutes from the minimum torque.

Tc90 (min) is the time to attain 90% of the MH−ML (dN-m) cure state inminutes, from the minimum torque.

Abbreviations Used in the Examples

Chimmasorb® 944 ispoly[[6-[(1,1,3,3-tetramethylbutyl)amino]-s-triazine-2,4-diyl]-[(2,2,6,6-tetramethyl-4-piperidyl)imino]-hexamethylene-[(2,2,6,6-tetramethyl-4-piperidyl)imino]],a HALS available from BASF.

CLD-80 is N,N′-Caprolactam disulfide (80%); Rhenogran® CLD-80 availablefrom Rhein Chemie.

CN9102® is an aliphatic allyl urethane available from Sartomer.

DTDM is 4,4′-dithiodimorpholine.

EVA is poly(ethylene vinyl acetate).

Evatane® 3345 is poly(ethylene vinyl acetate), 33 wt % vinyl acetate and45 MFI available from Arkema.

HVA-2 is N, N′-m-phenylene dimaleimide (coagent) available from DuPont®.

4-Hydroxy TEMPO or 4-OHT is4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl.

Irgafos® 168 is tris(2,4-di-tert-butylphenyl) phosphite, CAS#31570-04-4,available from BASF.

Kleenex® is facial tissue available from Kimberly-Clark.

Luperox® 101 is 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (93% to 95%peroxide content) available from Arkema.

Luperox® 101XL45 is 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (45%-48%peroxide content) available from Arkema on inert filler.

Luperox® 231XL40 is 3,3,5-trimethyl-1,1-di(t-butylperoxy)cyclohexane(40% peroxide content) available from Arkema.

Luperox® F40KEP is m/p-di(t-butylperoxy)diisopropyl benzene (40%peroxide content) available from Arkema.

Luperox® F90P is m/p-di(t-butylperoxy)diisopropyl benzene (90% peroxidecontent) available from Arkema.

Luperox® TBEC is t-butyl-2-ethylhexyl)monoperoxycarbonate.

MBT is mercaptobenzothiazole.

MBTS is benzothiazyl disulfide, also called mercaptobenzothiazoledisulfide, also called Altax® from R. T. Vanderbilt.

MTBHQ is mono-tertiary butyl hydroquinone, CAS 1948-33-0.

Naugard® 445 is 4,4′-bis(α-dimethylbenzyl)diphenylamine, an antioxidantfrom Chemtura.

PEG is Poly(ethylene glycol).

phr means parts of ingredient added for every 100 parts of rubber in theformulation.

Primol® 352 is a white oil (100% non-aromatic) from ExxonMobil.

Poly(ethylene α-olefin) is a Poly(ethylene octene) copolymer from Dowmarketed as Engage®

SR-350 or TMPTMA is a crosslinking coagent; or trimethylolpropanetrimethacrylate from Sartomer Arkema.

SR-351 is a crosslinking coagent; trimethylolpropane triacrylate fromSartomer Arkema.

Sunpar® 2280 is a paraffinic type process oil from Sunoco.

Tinuvin® 770 is bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate, a HALSavailable from BASF.

TMTD is tetramethylthiuram disulfide.

TAC is triallyl cyanurate a crosslinking coagent from Evonik.

TAIC is triallyl isocyanurate a crosslinking coagent from MitsubishiIntl.

TMPTMA is a crosslinking coagent; Sartomer SR-350; or trimethylolpropanetrimethacrylate from Sartomer Arkema.

TMQ or Stanguard® TMQ Powder is 2,2,4-trimethyl-1,2-dihydroquinoline,CAS#26780-96-1 from Harwick Standard Distribution Corporation.

TPP is triphenyl phosphite, CAS 101-02-0.

Vamac® DP, is a peroxide curable poly(ethylene acrylic) elastomer fromformerly DuPont, now called Chemours

Vanfre® VAM is Polyoxyethylene octadecyl ether phosphate a recommendedprocessing aid for the elastomer, VAMAC® DP an ethylene/acryliccopolymer,

Vanfre® VAM is available from R. T. Vanderbilt.

Vultac® 5 is t-amyl phenol disulfide polymer, an arylpolysulfidepolymer/oligomer also referred to as a poly(t-amylphenol disulfide);available from Arkema.

Vultac® 7 is t-butyl phenol disulfide polymer, an arylpolysulfidepolymer/oligomer available from Arkema.

Tests and Procedures Procedure for Mixing Rubber and Rubber SheetPreparation

The following procedure was used for mixing rubber and preparing therubber sheet for hot air curing. A Brabender Plasti-Corder® with a 50 mlcapacity bowl that is jacketed with the ability to run room temperatureor heated oil was used. The mixer was equipped with removable sigma typeblades. Using the specific gravity provided with the pre-compoundedelastomer, small strips of rubber were slowly added to the bowl at amixing speed of 20 to 25 rpm. The total amount of rubber added to theBrabender Plasti-Corder® bowl was equivalent to the weight needed toprovide 48 ml of rubber volume so that there was sufficient volume toadd the peroxide curatives to the rubber, as the mixer has a ˜50 mlvolume capacity.

Out of this 48 ml of rubber, two small strips of rubber (equivalent toabout 4 grams or no more than 5 ml) were held in reserve. All the restof the rubber was slowly added to the bowl. Once all the rubber wasadded to the mixer and the rubber was flowing in the bowl, the mixer rpmwas reduced to 15 rpm and the peroxide formulation for that experiment,which was pre-weighed in small Dixie® cups on a minimum of a three placebalance for good accuracy, was slowly added to the mixing rubber. Tomake sure all of the residual peroxide was included in the mixingrubber, the two small reserve rubber strips were used to wipe the powderoff the V-shaped metal portion of the mixer. This powder adhered to therubber strip and the remaining two strips of rubber were introduced intothe mixer.

The rpm was then increased back to 25 rpm for three minutes. After thistime, the mixer speed was lowered to 10 rpm and the mixer head wasunbolted and removed. Once the blades were no longer turning, the rubberaround the blades was safely removed and placed on a sheet of Mylar®polyester. There was a small amount of rubber that was located at thehead of the mixer blades within the inner hollow portion of the mixingchamber, which was removed last. The mixer head was re-assembled withthe bolts and the mixer motor was started again at 20 rpm. The rubberwhich was removed last, which was trapped in the mixing chamber, wasadded first to the spinning blades, followed by the rubber that wastaken off the blades. This provided for a more uniform mixing ofelastomer. The rpm was then increased to 25 rpm and held there for 3minutes. After this time, the mixer speed was set to 10 rpm and themixer head unbolted and removed. Once removed, the mixer blade motionstopped and it was again safe to remove all of the rubber from themixer's bowl and blades.

The warm rubber was then formed into a tight ball and placed between twoMylar® polyester sheets. This sandwich was placed in a warmed hydraulicpowered Carver press where the press may be set to between roomtemperature and 60° C., depending upon the elastomer and the peroxidecuratives being used. The ball of rubber was pressed flat between thetwo heavy Mylar® polyester sheets. Wearing nitrile gloves, the press wasopened and the Mylar® polyester sheet sandwich containing the flattenedrubber was removed. The top sheet was removed and the rubber was rolledinto a tube. This was re-sandwiched and flattened again. The sheet wasrolled again, but 90 degrees to the original roll direction, andflattened again. This was repeated a third time, and care was taken toflatten to an approximate thickness of ⅛ inch. The sandwich was placedon the bench top and covered with a metal sheet where the rubber wasallowed to cool. It was then removed and stored in a tightly-sealedpolyethylene bag. These sheets were then cut with scissors or using asharp metal circle punch, to make small flat circle sheets of uncuredrubber for the Rheometer cure evaluation, and square flat sheets for thehot air oven testing using the “Facial Tissue Paper Test” describedbelow.

Facial Tissue Paper Test

The following procedure was used to test the surface tack of the rubbersheet after curing in a hot air oven. This procedure is also referred toas a “Facial Tissue Paper Test” for surface tackiness of a rubber sheetcured in a hot air oven.

A flat sheet of uncured rubber was prepared with dimensions of ⅛″ thickby 2″ wide and 3″ long, and was hung carefully in a pre-heated hot airoven set to 205° C. for 15 minutes. The sheet was hung in the oven bymetal clamps from a metal rack to expose all sides of the sheet to thehot air. After 15 minutes of cure, the rubber sheet was promptly removedand placed on an aluminum foil-covered piece of cardboard. It wascovered immediately with a Kleenex® Facial Tissue and very firm pressurewas immediately applied by hand to the entire rubber surface, followedby applying a 1800 gram weight for five minutes. After the rubber cooledto room temperature, the soft facial tissue paper was carefully removedto examine the rubber surface for any tissue paper fibers that may haveadhered to the surface. If a great many tissue paper fibers adhere, thisindicates a poor surface cure, or one that has a high amount of surfacetackiness.

As used herein, the Surface Tackiness Number=(% of surface with no paperfibers÷10). The Surface Tackiness number can range from 10 to 0. Acompletely tack-free cured rubber surface with no tissue paper fibershas a rating of 10. A very poorly cured rubber surface that iscompletely covered in tissue paper fibers is rated a 0. If 90% of thesurface has no tissue paper fibers attached, the rating is a 9, if 70%of the surface has no tissue paper fibers attached, the rating is a 7,etc.

Rheometer Procedures

The following procedure was used for moving die rheometer and RPA(Rubber Process Analyzer) evaluations. For the Alpha Technologies MDRrheometer, test method ASTM D5289-12 “Standard Test Method for RubberProperty—Vulcanization Using Rotorless Cure Meters” was used. Testmethod ASTM D6204 was used with either a 0.5 degree or 1.0 degree arcand 100 cpm frequency of oscillation at cure temperatures appropriatefor the curative system, e.g., 185° C. for the examples below.

When conducting rheometer evaluations, approximately 5 to 6 grams ofelastomer (depending upon the density of the final compound) were usedto completely fill the upper and lower dies of the rheometer. Theuncured rubber was cut from the pressed sheet formed by the proceduredescribed above. The rubber was cut into small round discs about 1.25inches in diameter and placed between two Dartek® sheets. This sandwichwas then placed in the rheometer for testing following ASTM D5289.

Following ASTM D6601 for after cure dynamic testing, a test with the RPAusing the stress relaxation feature of the instrument with a 3 degreearc applied strain was applied to gauge the crosslinked elastomer'sability to serve as a gasket or seal. This purpose was very similar tothe percent compression test following standard NF ISO 815. The loss ofthe elastic modulus or S′ (dN-m) is followed versus time, for severalminutes. The rate in loss of elastic modulus reflects the percentcompression set performance. The lowest percent compression values forcured rubber samples will have the lowest loss in the elastic modulus orS′ (dN-m) over a one minute period at a test temperature of 185° C. orhigher.

% Compression Set Procedures

The following procedures were used for compression set evaluations. Thestandardized test methods for % compression set were NF ISO 815 and/orASTM D395, which are suitable for Ambient and High Temperatureapplication testing. Specifically, in Example 1, NF ISO 815 was used,wherein samples for the test were first cured at 190° C. to form acylinder of 6.3±0.3 mm height and 13±0.5 mm diameter using a curing timeof Tc90+8 minutes, then test pieces were placed in the NF ISO 815 deviceto compress 25% at 150° C. for 24 hours. After this time, samples werereleased and placed on a wooden board at ambient temperature for 30minutes before being measured for change in height.

Tensile Testing Procedures

The following procedures were used for tensile testing. Tensileproperties were determined by following the standard NF ISO 37 and/orASTM D412. First, sheets of 1.5 mm thick were cured under pressure in apneumatic press. The conditions of curing were determined from the Tc90(minute) 90% of cure time result for the compound when tested on the MDRor RPA rheometer at 190° C. The curing temperature was 190° C. and thecuring time was Tc90+8 minutes. Then, dumbbells were cut from the 1.5 mmcured sheet using the appropriate die designated by NF ISO 37 and/orASTM D412. Finally, tensile tests were performed on the dumbbells usingan INSTRON® 5565 tensile machine. A speed of 200 mm/min was used.

EXAMPLES Example 1

In this example, the EDPM Masterbatch elastomer formulation in Table 1and the sulfur vulcanization “control” formulation in Table 2 wereprepared. Table 3 provides a summary of five sample runs, which testedvarious cure systems in the EPDM masterbatch formulation.

TABLE 1 “EPDM MB” Masterbatch Formulation Ingredient Phr Vistalon ® 2504EPDM 100.0 N550 Carbon Black 100.0 Primol ® 352 white process oil 40.0PEG Polyethylene glycol 3.0 Stanguard ® TMQ Powder (antioxidant) 1.0Total weight of the masterbatch 244.0

TABLE 2 Sulfur Vulcanization Control Formulation used to Cure “EPDM MB”found in TABLE 1 Masterbatch Ingredient Parts “EPDM MB” 244.0 NOTE: 244PARTS OF “EPDM MB” CONTAINS 100 PARTS OF RUBBER “Sulfur Control”Ingredients PHR (Parts Per 100 Rubber) Zinc Oxide 5.00 Stearic Acid 1.00Sulfur (80%) 3.10 MBTS (75%) 2.20 MBT (80%) 1.64 TMTD (80%) 0.31 TotalSulfur Control = 13.25

TABLE 3 Sulfur and Peroxide Formulation Testing of TABLE 1 EPDMMasterbatch Sample # 1 2 3 4 5 Parts of “EPDM MB” from Table 1 244 244244 244 244 phr “Sulfur Control” from Table 2 13.25 — — — — phr HVA-2 ®— — 2.0 — — phr Luperox ® F40KE — 8.0 — — — phr Luperox ® F90P — — 4.05.28 4.0 phr Vultac ® 5 — — 1.6 2.16 3.6 phr MBTS — — 0.4 0.56 0.4 phrTotal Curative 13.25 8.0 8.0 8.0 8.0 Moving Die Rheometer at 180° C.,1.677 Hz (100 cpm), 0.5° arc Crosslink Density (MH − ML) in dN-m 27.527.5 21.25 28.0 22.5 Hot Air Cure at 205° C. for 15 minutes SurfaceTack: 10 2.8 9.6 9.8 9.9 10 = NO tack; 0 = 100% sticky Physical Testingof Cured Elastomer Tensile Strength at Break (MPa) 18.0 16.1 10.4 16.516.1 % Elongation at Break 229 169 197 207 331 % Compression Set at 150°C. for 24 hours 93 24 51 31 72

Sample #1 used the sulfur vulcanization “control” formulation describedin TABLE 2. When 13.25 phr of total curative was utilized, no surfacetackiness was observed (rating of 10 out of 10) after curing theelastomer in a hot air oven at 205° C. for 15 minutes. However, a verypoor % compression set of 93% was observed. A 100% compression setrepresents a total and complete deformation under heat and stress, so a93% value is nearly a complete failure for a sealing application, andreveals the poor heat-aging nature when such resins are subjected tosulfur vulcanization.

Sample #2 used a conventional organic peroxide Luperox® F40KE at 8.0 phras the cure system in the EPDM masterbatch. The EPDM masterbatch curedwith this standard peroxide exhibited considerable surface tackinesswith a very poor rating of 2.8 out of a possible 10, after the 205° C.and 15 minute hot air oven cure process, and an excellent % compressionset value of 24%.

Sample #3 used a formulation taught by U.S. Pat. No. 6,747,099, whichincludes HVA-2 (N, N′-m-phenylene dimaleimide) coagent to achieve atack-free surface, along with an organic peroxide and a sulfurcontaining compound. Curing in a hot air oven at 205° C. for 15 minutesprovided a good surface rating of 9.6 out of 10, but this formulationonly provided an intermediate 51% compression set value in this EPDMcompound.

Sample #4 used an organic peroxide formulation of the present invention,which does not include the expensive and toxic HVA-2 coagent required inprior art formulations. Sample #4 demonstrated unexpected physicalproperties with the use of select disulfide compounds and at least oneorganic peroxide. At only 8.0 phr total curative, Sample #4 provided aslightly higher crosslinking (MH−ML) in dN-m of the EPDM compared to theSample #1 sulfur control, with an excellent tack-free surface curerating of 9.8 out of 10 and a very unexpected low % compression setvalue of 31%, which outperformed the prior art sample #3 value of 51%.Sample #4 provided the lowest % compression set of all the samplestested in this example. This was highly unexpected, as the HVA-2 coagentis widely used for increasing organic peroxide crosslinking performanceand lowering the compression set of crosslinked elastomers. Sample #4provided a better hot air oven surface cure, higher crosslink density, asignificantly higher (58% higher) tensile strength at break, and a lower% compression set. Sample #4 also unexpectedly provided 5% longer %Elongation at break, despite the higher crosslink density generated bythis formulation, compared to Sample #3.

Sample #5 used an organic peroxide formulation of the present invention.Sample #5 further improved the hot air surface cure performance with anearly perfect 9.9 rating out of 10. The crosslink density, surfacetackiness, tensile strength and % elongation outperformed the prior artSample #3. Sample #5 also had a significantly improved % compression setcompared to the sulfur control, Sample #1. The % elongation was improvedby 44% (331% vs. only 229%), which was highly unexpected.

Example 2

In this example, organic peroxide formulations were used to hot air curea blend of EPDM and a poly(ethylene α-olefin) copolymer. EPDM cancontain from roughly 5% and up to 9% unsaturation, both of which can becrosslinked by sulfur vulcanization. However, sulfur vulcanization curesystems cannot cure saturated polyethylene copolymers like EVA orpoly(ethylene α-olefin) copolymers. TABLE 4 provides the genericformulation that was used to evaluate a 54% and 46% blend of an EPDM andpoly(ethylene α-olefin) copolymer.

TABLE 4 “EPDM + EP Masterbatch” EPDM 54 Poly(ethylene-α-olefin) 46Carbon Black & Fillers 240 Process Oil 89 Total Ingredients 429

TABLE 5 Standard and Novel Peroxide Formulation testing of TABLE 4“EPDM + EP Masterbatch” Sample # 1 2 3 4 5 6 Table 4 “EPDM + 429 429 429429 429 429 EP Masterbatch phr Vul-Cup ® 5.0 5.0 5.0 5.0 5.0 6.0 40KEphr HVA-2 ® 2.5 — — — — — phr TMPTMA — — — — — 3.0 phr Vultac ® 5 2.0 —— 4.5 — — phr MBTS 0.5 0.67 0.67 0.67 0.67 — phr DTDM — 4.5 — — — — phrVultac ® 7 — — — — 4.5 — phr CLD-80 — — 4.5 — — — phr total curative10.0 10.17 10.17 10.17 10.17 9.0 RPA Rheometer 185° C., 1° arc, 100 cpm,(1.677 Hz) MH (dN-m) 10.41 13.22 12.37 11.87 11.82 15.13 MH − ML (dN-m)8.56 11.70 10.97 10.36 10.36 13.56 Ts1 (mm) 0.41 1.20 0.84 0.67 0.790.58 Ts2 (mm) 0.53 1.95 1.26 0.90 1.10 0.77 Tc50 (min) 0.85 3.46 2.741.66 2.19 1.43 Tc90 (min) 2.71 5.13 7.35 3.83 5.87 3.17 Hot Air OvenCure at 205° C. for 5 minutes Surface Tack: 10 = 0 10 10 8 9.5 0 notack; 0 = 100% tacky

Sample 1 used a formulation taught by U.S. Pat. No. 6,747,099, whichincludes the coagent HVA-2, along with an organic peroxide and a sulfurcontaining compound. HVA-2 is a fast-reacting coagent which results in afaster crosslinking reaction, thus shorter ts1 and ts2 scorch times,which can make mixing the elastomer more difficult. This Sample 1formulation provided no improvement in surface tackiness over thestandard peroxide of Sample 6. Both the prior art organic peroxideformulation (Sample 1) and the standard organic peroxide cure system(Sample 6) provided a poor surface cure rating of 0.

The standard peroxide cure system in Sample 6 provided the highestamount of crosslinking (MH−ML) in dN-m, which shows that the amount ofcrosslinking of the rubber has little to do with oxygen inhibition ofcrosslinking at the rubber surface.

In contrast, Samples 2, 3, 4 and 5, which used organic peroxideformulations of the present invention, provided excellent surface cureperformance with ratings of 10, 10, 8 and 9.5, respectively, in the EPDMand poly(ethylene α-olefin) copolymer blend. Furthermore, thesecompositions provided unexpectedly longer scorch times, based on Ts1 andTs2 minutes values. Longer scorch times are desirable for continuousextrusion operations.

Example 3

In this example, organic peroxide formulations were used to hot air curepoly(ethylene vinyl acetate) (EVA). One of the main advantages oforganic peroxide cure systems is their ability to crosslink fullysaturated polymers. One such useful polymer is poly(ethylene vinylacetate) or EVA. As shown in TABLE 6, an organic peroxide formulation ofthe present invention, labeled “SYSTEM-F90,” was used to cure EVA in ahot air oven at 205° C. for 15 minutes, and was compared to a standardorganic peroxide formulation consisting of only Luperox® F40KEP.

TABLE 6 “SYSTEM-F90” Luperox ® F90P 66.67% Vultac ® 5 26.67% MBTS  6.66%

The “SYSTEM-F90” peroxide formulation was tested to see if it couldsuccessfully hot air cure the EVA Elastomer formulation described inTABLE 7, which is a fully saturated polymer that cannot be sulfur cured.The EVA Elastomer formulation was cured in a hot air oven at 205° C. for15 minutes with the “SYSTEM-F90” formulation (2.125 phr), and withLuperox® F40KEP (2.125 phr). Crosslinking the EVA sheet in a hot airoven provided a significantly improved cured surface with SYSTEM-F90,which had a surface tackiness rating of 9.5 in accordance with theFacial Tissue Paper Test, compared to the standard peroxide Luperox®F40KEP, with a surface tackiness rating of 6.0 using the Facial TissuePaper Test.

TABLE 7 EVA Elastomer Formulation Phr Evatane ® 3345PV 100 N550 carbonblack 100 Primol ® 352 process oil 40 Polyethylene glycol 3 Stanguard ®TMQ Powder 1 Total 244

Example 4

In this example, organic peroxide formulations were used to hot air curethe “EPDM MB” rubber compound described in TABLE 1. The organic peroxideformulations were similar to the “SYSTEM-F90” formulation provided inTABLE 6, except the Luperox® F90P component was replaced with otherperoxides to produce “SYSTEM-101”, “SYSTEM-DCP” and “SYSTEM-231”formulations shown in TABLE 8, while keeping the other additives thesame. The peroxide concentration used in each formulation was adjustedon an equal active oxygen content using Luperox® F90P as the control.

TABLE 8 Examples of Organic Peroxide Formulations for CrosslinkingElastomers in a Hot Air Oven, as Taught in Embodiments of this InventionSYSTEM- SYSTEM- SYSTEM- SYSTEM- Formulation name F90 101 DCP 231 Partsper 100 rubber phr phr phr phr Luperox ® F90P 5.336 — — — Luperox0 ®101XL45 — 8.751 — — Di-Cup ® R — — 7.416 — Luperox ® 231XL40 — — —10.417 Vultac ® 5 2.136 2.136 2.136 2.136 MBTS 0.528 0.528 0.528 0.528Hot Air Oven Cure at 205° C. for 15 minutes Surface Tack: 10 = no 10 1010 10 tack; 0 = 100% tackyThese peroxide formulations listed in TABLE 8 were blended into the“EPDM MB” compound listed in TABLE 1, at the phr loadings provided inTABLE 8. The compounded EPDM sheets containing each of these peroxideswere hot air cured in an oven using the standard procedure describedherein, i.e., at 205° C. for 15 minutes. It was found that all of theperoxide formulations presented in TABLE 8 unexpectedly provided atack-free surface after being cured in the hot air oven. This wasdetermined based upon the lack of facial tissue paper adhering to thehot rubber surface, in accordance with the Facial Tissue Paper Test. Incontrast, curing the same rubber sheet composition with only thecorresponding standard peroxides (i.e., with formulations that includedonly the peroxide without the additives Vultac® 5 and MBTS) resulted innearly complete covering of the rubber surface with tissue paper,indicating a poor surface cure.

Example 5

In this example, organic peroxide formulations were used to hot air curethe EPDM elastomer masterbatch described in TABLE 1. It was unexpectedlyfound that organophosphites blended with Luperox® F40KEP resulted in asubstantially tack-free surface when crosslinking in a hot air oven, asshown in TABLE 9. The EPDM elastomer masterbatch is described in TABLE 1and the sulfur control is described in TABLE 2. The data in TABLE 9(particularly Sample #'s 4, 6, 7 and 8, which had substantiallytack-free surfaces) illustrate the effectiveness of the organophosphitesin providing surfaces with less tackiness than the standard peroxideshown in Sample #2, TABLE 9.

TABLE 9 Effect of Phosphite Additives on Surface Tackiness when usingOrganic Peroxides Curing EPDM in a Hot Air Oven at 205° C., 15 minSample # 1 2 3 4 5 6 7 8 EPDM Masterbatch 244 244 244 244 244 244 244244 (Table 1) parts phr Sulfur Cure 13.25 — — — — — — — (Table 2) phrLuperox ® — 8.0 8.0 8.0 8.0 8.0 8.0 8.0 F40KEP phr Irgafos ® 168 — — 1.03.0 5.0 — — — phr TPP (triphenyl — — — — — 1.0 3.0 5.0 phosphite) RPARheometer Cure at 185° C., 1° arc, 100 cpm (1.667 Hz) MH − ML (dN-m)26.78 28.30 26.31 21.83 18.18 26.00 16.46 9.67 Hot Air Oven Cure at 205°C., 15 minutes, then Surface Tack Testing with Facial Tissue SurfaceTack: 10 = 10 0 7.5 8.4 7.2 8.8 8.7 9.2 no tack; 0 = 100% tacky

Example 6

In this example, organic peroxide formulations were used to hot air curethe EPDM elastomer masterbatch described in TABLE 1. It was unexpectedlyfound that HALS (Hindered Amine Light Stabilizers) blended with Luperox®F40KEP resulted in a substantially tack-free surface when crosslinkingin a hot air oven, as shown in TABLE 10. The EPDM elastomer masterbatchis described in TABLE 1 and the sulfur control is described in TABLE 2.The data in TABLE 10 show that the use of various HALS (particularly inSample #'s 4, 7 and 8) provided a better cure performance (MH−ML indN-m) and surfaces with less tackiness compared to the standard peroxideshown in Sample #2, TABLE 10.

TABLE 10 Effect of Hindered Amine Light Stabilizer Additives on SurfaceTackiness when using Organic PeroxidesCuring EPDM in a Hot Air Oven at205° C., 15 mm Sample # 1 2 3 4 5 6 7 8 Parts EPDM 244 244 244 244 244244 244 244 Masterbatch Table 1 phr Sulfur Cure 13.25 — — — --- --- — —(Table 2) phr Luperox ® — 8.0 8.0 8.0 8.0 8.0 8.0 8.0 F40KEP phrTinuvin ® 770 — — 1.0 3.0 5.0 — — — phr Chimassorb ® — — — — — 1.0 3.05.0 994 RPA Rheometer Cure at 185° C., 1° arc, 100 cpm (1.667 Hz) MH −ML (dN-m) 26.78 28.30 27.13 25.20 24.40 26.72 24.53 22.63 Hot Air OvenCure at 205° C., 15 minutes, then Surface Tack Testing with FacialTissue Surface Tack: 10 = 10 0 6.5 8.5 6.5 5.0 9.0 8.0 no tack; 0 = 100%tacky

Example 7

In this example, organic peroxide formulations were used to hot air curethe EPDM elastomer masterbatch described in TABLE 1. It was unexpectedlyfound that CN9102® aliphatic allyl urethane blended with Luperox® F40KEPresulted in a substantially tack-free surface when crosslinking in a hotair oven, as shown in TABLE 11.

TABLE 11 CN9102 ® aliphatic allyl urethane is capable of providing atack-free surface when curing elastomers in the presence of hot air withorganic peroxides Curing EPDM in a Hot Air Oven at 205° C., 15 minSample # 1 2 3 EPDM Masterbatch (from Table 1) parts 244 244 244 phrVul-Cup ® 40KE 6.0 6.0 6.0 phr CN9102 ® from Sartomer 3.0 6.0 10.0 RPARheometer Cure at 185° C., 1° arc, 100 cpm (1.667 Hz) ML (dN-m) 1.331.28 1.18 MH (dN-m) 15.47 16.55 13.45 MH − ML (dN-m) 26.78 28.30 27.13Ts1(min) 0.46 0.46 0.50 Tc90 (min) 1.59 1.62 1.64 Hot Air Oven Cure at205° C., 15 minutes, then Surface Tack Testing with Facial TissueSurface Tack: 10 = no tack; 0 = 100% tacky 9.8 8.5 10

Example 8

In this example, illustrated in TABLE 12, a monoperoxycarbonate typeorganic peroxide (Luperox® TBEC) was blended with sulfur-containingcompounds to cure the EPDM Masterbatch of Table 1 in hot air. Thisperoxide formulation unexpectedly provided a tack-free surface with a 10rating (completely tack-free) after curing in the hot air oven. Luperox®TBEC decomposes faster than Vul-Cup® 90 due to the lower half-life at185° C., however the advantage is the significantly shorter cure time(Tc90 minutes).

TABLE 12 Using Luperox ® TBEC to provide a tack-free surface in thepresence of atmospheric oxygen when curing EPDM in a Hot Air Oven at205° C. for 15 min, as per the practice of our invention Sample # 1 2 3EPDM Masterbatch (from Table 1) parts 244 244 244 phr Vul-Cup ® 90P 5.614.75 — phr Luperox ® TBEC — — 9.0 phr Vultac ® 5 — 1.9 2.7 phr MBTS 0.470.70 RPA Rheometer Cure at 185° C., 1° arc, 100 cpm (1.667 Hz) MH − ML(dN-m) 34.72 25.04 14.98 Tc90 (min) 3.31 3.03 0.40 Hot Air Oven Cure at205° C., 15 minutes, then Surface Tack Testing with Facial TissueSurface Tack: 10 = no tack; 0 = 100% tacky 0 10 10

Example 9

In this example, scorch time was increased while providing a desirabletack-free surface cure of an EPDM compound in a hot air oven (at 205°C., 15 min) when using organic peroxide formulations of the presentinvention. A longer scorch time, higher amount of crosslinking, andshorter cure time were obtained with the synergistic blend of 4-hydroxyTEMPO and MTBHQ with sulfur-containing compounds and Luperox® F90P.

The unexpected synergy may be described by using the equation:EFFICIENCY=[(MH−ML)×Ts2]÷(Tc90−Ts2),

where a higher efficiency value indicates a higher efficiency of scorchtime with respect to the effect on state of cure and cure time for theperoxide formulation.

TABLE 13 Increasing Scorch Time while Providing a Tack-free Surface Cureusing Organic Peroxides to Cure EPDM in a when Hot Air Oven at 205° C.,15 min Sample # 1 2 3 4 5 6 Parts EPDM MB 244 244 244 244 244 244 Table1 phr Sulfur Cure 13.25 — — — — — (Table 2) phr Luperox ® — 5.61 4.314.88 4.88 4.88 F90P phr Vultac ® 5 — — 1.72 1.95 1.95 1.95 phr 4-hydroxy— — — 0.92 0.46 — TEMPO phr MTBHQ — — — — 0.46 0.92 phr MBTS — — 0.430.48 0.48 0.48 RPA Rheometer Cure at 185° C., 1° arc, 100 cpm (1.667 Hz)Ts2 scorch time 0.73 0.39 0.51 0.56 0.67 0.72 (min.) Tc90 (minutes) 6.173.31 3.03 3.19 3.39 3.50 MH − ML 22.31 34.72 25.04 20.77 21.13 18.83(dN-m) EFFICIENCY 2.99 4.64 5.07 4.42 5.20 4.88 Hot Air Oven Cure at205° C., 15 minutes, then Surface Tack Testing with Facial TissueSurface Tack: 10 = 10 0 10 9.8 10 9.8 no tack; 0 = 100% tacky

The formulation provided in Sample #5 of TABLE 13 provides a hugeEFFICIENCY value of 5.20 versus only 2.99 for the sulfur cure controlprovided in Sample #1. The increased scorch time with respect to curetime for Sample #5 was achieved by the blend of 0.46 phr 4-hydroxy TEMPOwith 0.46 phr MTBHQ for a total of 0.92 phr for the 50:50 blend. ThisEFFICIENCY of 5.20 is larger than the 4.42 value obtained by Sample #4with the use of 0.92 phr 4-hydroxy TEMPO, and also larger than 4.88 forSample #6 with the use of 0.92 phr MTBHQ. Furthermore, the final hot airoven cured surface for Sample #5 was higher, with a score of 10 (i.e.,completely tack-free). Thus, Sample #5 of TABLE 13 provides not only acompletely tack-free surface when cured in the presence of atmosphericoxygen using a hot air oven, but a desirable longer scorch time forbetter extrusion and processing prior to cure.

One advantage of the present invention peroxide formulations is theability to utilize existing sulfur cure processing and crosslinkingequipment that are currently present in manufacturing plants, whilebeing able to replace sulfur cure with an organic peroxide with littleto no adjustments to the manufacturing operations. The added benefit isimproved productivity, by reducing cycle time due to the lower Tc90,while significantly improving the crosslinked rubber's physicalproperties. The carbon-carbon bond crosslinks generated by an organicperoxide enables one to better utilize all the engineering capabilitiesof the elastomer, as this is a structure that exists in the polymerbackbone itself.

Example 10 Curing Vamac® DP, a Poly(Ethylene Acrylate) Copolymer in 200°C. Hot Air Oven for 15 Minutes

TABLE 14 Run # 1 2 DuPont VAMAC ® DP 100.00 100.00 N550 carbon black87.00 87.00 Chemtura Naugard ® 445 1.00 1.00 Stearic Acid 0.50 0.50 R.T. Vanderbilt Vanfre ® VAM 0.50 0.50 Arkema Di-Cup ® 40C 6.00 5.89Arkema MLPC, Vultac ® 5 0.00 0.09 R. T. Vanderbilt Altax ® (MBTS) 0.000.02 72% TAIC on silica 2.00 0.00 Sartomer SR-350 (TMPTMA) 0.00 1.75 RPA173 C., 1° arc, 100 cpm: MH (dN-m) 17.90 20.40 Crosslinking in a 200° C.hot air oven for 15 minutes, followed by the tackiness test. FacialTissue Tackiness Test where: 0 8 10 = no tack; 0 = 100% tacky

In Example 10, TABLE 14 shows crosslinking of a poly(ethylene acrylate)elastomer called Vamac® DP. Using a novel blend (Run #2) of dicumylperoxide, Vultac® 5 a poly(t-amylphenol disulfide), MBTS(mercaptobenzothiazole disulfide), and TMPTMA (trimethylolpropanetrimethacrylate) the elastomer is crosslinked in a hot air oven at 200°C. for 15 minutes, providing a very good cured surface with a rating of8 out of 10 based on the facial tissue paper test. The standard peroxidesystem (Run #1) which uses a coagent TAIC provided a sticky surface witha rating of 0 out of 10.

Example 11 Curing EPDM Elastomer in 205° C. Hot Air Oven for 15 Minutes

TABLE 15 Run # 1 2 ExxonMobil Vistalon ®2504 EPDM 100.00 100.00 N550Carbon Black 270.00 270.00 Sunpar ® 2280 process oil 160.00 160.00Stanguard ® TMQ Powder antioxidant 2.00 2.00 Arkema Luperox ® F90P 0.004.66 Arkema Luperox ® 101 9.33 4.66 Arkema MLPC Vultac ® 5 3.73 3.73 R.T. Vanderbilt Altax ® (MBTS) 0.94 0.94 RPA, 200° C., 1° arc, 100 cpm: MH(dN-m) 7.64 4.25 Hot air oven curing @205° C. for 15 minutes followed bythe tack test Facial Tissue Tackiness Test where: 10 10 10 = no tack; 0= 100% tacky

In this example an EPDM formulation is cured using two novel peroxideblends as taught in the practice of our invention. The first peroxidecomposition (Run #1), is a novel blend of Luperox® 101 whose chemicalname is 2,5-dimethyl-2,5-di(t-butylperoxy)hexane with Vultac® 5 andMBTS. The second composition (Run #2), is a novel blend of Luperox® F90Pwhose chemical name is m/p-di(t-butylperoxy)diisopropylbenzene, Luperox®101 whose chemical name is 2,5-dimethyl-2,5-di(t-butylperoxy)hexane,together with Vultac® 5 and MBTS. Both of these novel formulationsresulted in a fully cured surface when the elastomer was cured in a hotair oven at 205° C. for 15 minutes.

Example 12 Curing EPDM Elastomer in 205° C. Hot Air Oven for 15 Minutes

TABLE 16 Sample # 1 2 3 Parts EPDM MB Table 1 244 244 244 phr Luperox ®F90P 3.85 3.85 3.85 phr Vultac ® 5 1.54 1.54 1.54 phr MBTS 0.38 0.380.38 phr 4-OHT 0.36 0.36 0.36 phr MTBHQ 0.36 0.36 0.36 phr TAC (triallylcyanurate) 1.20 — — phr TAIC (triallyl isocyanurate) — 1.20 — phr TMPTMA(trimethylolpropane — — 1.20 trimethacrylate) RPA Rheometer Cure at 185°C., 1° arc, 100 cpm (1.667 Hz) 15 minutes ML (dN-m) 1.32 1.30 1.31 MH(dN-m) 19.41 19.52 23.69 MH − ML (dN-m) 18.09 18.21 22.38 Tsl scorchtime (min.) 0.55 0.55 0.56 Ts2 scorch time (min.) 0.70 0.70 0.71 Tc50(minutes) 1.49 1.50 1.85 Tc90 (minutes) 3.47 3.46 4.14 Hot air ovencuring at 205° C. for 15 min, then the facial tissue testing. SurfaceTack: 10 = no tack; 0 = 100% tacky 10 10 10

Example 12 illustrates three novel peroxide blends which all providedexcellently cured EPDM elastomers with No Tack (rating 10 out of 10)wherein these novel peroxide blends had three things in common: Luperox®F90P, Vultac® 5, MBTS wherein the crosslinking coagent was either TAC,TAIC or TMPTMA, as part of the novel composition to increase the stateof cure while still providing a 100% tack-free hot air cured surface.

What is claimed is:
 1. An organic peroxide formulation comprising: at least one organic peroxide; at least one sulfur-containing compound, at least one nitroxide-containing compound, and at least one quinone-containing compound, wherein the formulation does not include any bis-, tri- or higher poly-maleimides, or bis-, tri- or higher poly-citraconimides, and wherein the amounts of the at least one organic peroxide, the at least one sulfur-containing compound, the at least one nitroxide-containing compound, and the at least one quinone-containing compound are selected such that the formulation is capable of curing an elastomer composition in the full or partial presence of oxygen.
 2. The organic peroxide formulation of claim 1, wherein the at least one sulfur-containing compound is selected from the group consisting of poly(t-amylphenol disulfide); poly(t-butylphenol disulfide); 4,4-dithiodimorpholine; benzothiazyl disulfide; N,N′-caprolactam disulfide; and a combination thereof.
 3. An elastomer composition comprising: at least one elastomer; and the organic peroxide formulation of claim 1 wherein the elastomer composition is curable in the full or partial presence of oxygen.
 4. A process for curing the elastomer composition of claim 3, said process comprising: curing said elastomer composition in the presence of oxygen.
 5. The organic peroxide formulation of claim 1 further comprising: one or more additional compounds selected from the group consisting of: organophosphite compounds, HALS compounds, aliphatic allyl urethane compounds, drying oils, cellulose compounds and a combination thereof, wherein the amounts of the components are selected such that the formulation is capable of curing an elastomer composition in the full or partial presence of oxygen.
 6. An elastomer composition comprising: at least one elastomer, and the organic peroxide formulation of claim
 5. 7. A process for curing the elastomer composition of claim 6, said process comprising: curing said elastomer composition in the presence of oxygen.
 8. The organic peroxide formulation of claim 1 further comprising: at least one crosslinking coagent selected from the group consisting of allyl methacrylate oligomer, triallyl cyanurate, triallyl isocyanurate, trimethyloylpropane trimethacrylate, trimethyloylpropane triacrylate, zinc diacrylate, and zinc dimethacrylate.
 9. The organic peroxide formulation of claim 1 comprising: at least one peroxide chosen from the group consisting of 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, t-butylperoxybenzoate, t-butyl-2-ethylhexylmonoperoxycarbonate, 2,5-dimethyl-2,5-di(t-butylperoxy)hexanem, dicumyl peroxide, m/p-di(t-butylperoxy)diisopropylbenzene, and t-butylcumylperoxide, and at least one sulfur-containing compound chosen from the group consisting of poly(t-amylphenol disulfide), N,N′-caprolactam disulfide and benzothiazyl disulfide.
 10. The organic peroxide formulation of claim 1 comprising: at least one peroxide chosen from the group consisting of 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, t-butylperoxybenzoate, t-butyl-2-ethylhexylmonoperoxycarbonate, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, dicumyl peroxide, m/p-di(t-butylperoxy)diisopropylbenzene, and t-butylcumylperoxide; at least one sulfur-containing compound chosen from the group consisting of poly(t-amylphenol disulfide), N,N′-caprolactam disulfide and benzothiazyl disulfide; and at least one crosslinking coagent selected from the group consisting of allyl methacrylate oligomer, triallyl cyanurate, triallyl isocyanurate, trimethyloylpropane trimethacrylate, trimethyloylpropane triacrylate, zinc diacrylate, and zinc dimethacrylate. 